Populate text box on panel scroll event

Dynamically creating textbox on panel scroll in vb.net
vb.net
Hi i am creating 10 text boxes and combo boxes as a row to populate a sales invoice screen. after user entering to the last text box dynamically created i am populating again 20 more rows and after user entering the 29th text box again i am creating 20 more rows and it goes untill 250 rows created, but i am stuck on which event should i write the code and serial number also i could not generate

Private Sub Panel1_Resize(sender As Object, e As System.EventArgs) Handles Panel1.Enter

Dim viewable As Boolean

If box5(9).Location.Y < Panel1.Height AndAlso box5(9).Location.Y + box5(9).Height > 0 Then

viewable = True

Panel1.HorizontalScroll.Visible = False
Dim x1 As Integer = 100
Dim y1 As Integer = 0
Dim MyLocationX As Integer = 175
Dim MyLocationY As Integer = 175
Dim k As Integer

For i As Integer = 0 To 90
For j As Integer = 11 To 90

box5(i) = New TextBox

box5(i).ReadOnly = True
box5(i).BackColor = Color.White

box5(i).Text = 10 + i

Next j
k = box5(i).Text
box5(i).Font = New Font("Times New Roman", 9)
box5(i).TabStop = False
box5(i).Location = New System.Drawing.Point(0, 200 + i * 20)
box5(i).Size = New System.Drawing.Size(55, 26.2)
box5(i).Multiline = True

AddHandler box5(i).TextChanged, AddressOf Qty_TextChanged

Panel1.Controls.Add(box5(i))



DropDownlist(i) = New ComboBox
DropDownlist(i).Name = (y1 + 1).ToString
DropDownlist(i).Location = New Point(55, 200 + i * 20)

DropDownlist(i).ImeMode = Windows.Forms.ImeMode.KatakanaHalf
DropDownlist(i).DropDownStyle = ComboBoxStyle.DropDown
DropDownlist(i).AutoCompleteSource = AutoCompleteSource.ListItems
DropDownlist(i).AutoCompleteMode = AutoCompleteMode.SuggestAppend
DropDownlist(i).Font = New Font("Times New Roman", 12)
DropDownlist(i).Size = New System.Drawing.Size(150, 50)
AddHandler DropDownlist(i).KeyDown, AddressOf dropdownsearch
AddHandler DropDownlist(i).GotFocus, AddressOf cbsearch
Panel1.Controls.Add(DropDownlist(i))
MyLocationY = MyLocationY + 60
y1 = y1 + 1





box6(i) = New TextBox
box6(i).BackColor = Color.White
box6(i).Font = New Font("Times New Roman", 12)
box6(i).Location = New System.Drawing.Point(199, 200 + i * 20)
box6(i).Size = New System.Drawing.Size(216, 22)
box6(i).ReadOnly = True
AddHandler box6(i).GotFocus, AddressOf combo_TextChanged1
Panel1.Controls.Add(box6(i))
Dim qty1(100) As Double

iname(i) = New TextBox
iname(i).Location = New System.Drawing.Point(412, 200 + i * 20)
iname(i).Size = New System.Drawing.Size(52, 22)
iname(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(iname(i))
AddHandler iname(i).LostFocus, AddressOf combo_TextChanged3
AddHandler iname(i).LostFocus, AddressOf combo_TextChanged66
AddHandler iname(i).LostFocus, AddressOf combo_TextChanged68
Dim rate1(100) As Double

exname1(i) = New TextBox
exname1(i).Location = New System.Drawing.Point(464, 200 + i * 20)
exname1(i).Size = New System.Drawing.Size(61, 22)
exname1(i).Font = New Font("Times New Roman", 12)
rate1(i) = Val(exname1(i).Text)
Panel1.Controls.Add(exname1(i))




box2(i) = New TextBox
box2(i).Location = New System.Drawing.Point(524, 200 + i * 20)
box2(i).Size = New System.Drawing.Size(70, 22)
box2(i).ReadOnly = False
box2(i).BackColor = Color.White
box2(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(box2(i))

gross(i) = New TextBox
gross(i).Location = New System.Drawing.Point(593, 200 + i * 20)
gross(i).Size = New System.Drawing.Size(85, 22)
gross(i).ReadOnly = False
gross(i).BackColor = Color.White
gross(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(gross(i))

disp(i) = New TextBox
disp(i).Location = New System.Drawing.Point(675, 200 + i * 20)
disp(i).Size = New System.Drawing.Size(45, 22)
disp(i).ReadOnly = False
disp(i).BackColor = Color.White
disp(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(disp(i))

net(i) = New TextBox
net(i).Location = New System.Drawing.Point(718, 200 + i * 20)
net(i).Size = New System.Drawing.Size(97, 22)
net(i).ReadOnly = False
net(i).BackColor = Color.White
net(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(net(i))

spc(i) = New TextBox
spc(i).Location = New System.Drawing.Point(814, 200 + i * 20)
spc(i).Size = New System.Drawing.Size(127, 22)
spc(i).ReadOnly = False
spc(i).BackColor = Color.White
spc(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(spc(i))

exdes(i) = New TextBox
exdes(i).Location = New System.Drawing.Point(939, 200 + i * 20)
exdes(i).Size = New System.Drawing.Size(170, 22)
exdes(i).ReadOnly = False
exdes(i).BackColor = Color.White
exdes(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(exdes(i))

fullfill(i) = New DateTimePicker
fullfill(i).Location = New System.Drawing.Point(1107, 200 + i * 20)
fullfill(i).Size = New System.Drawing.Size(100, 22)
fullfill(i).CustomFormat = "dd-MM-yy"
fullfill(i).Format = DateTimePickerFormat.Custom

fullfill(i).BackColor = Color.White
fullfill(i).Font = New Font("Times New Roman", 12)
Panel1.Controls.Add(fullfill(i))

If (String.IsNullOrEmpty(DropDownlist(i).Text)) Then

AddHandler DropDownlist(i).LostFocus, AddressOf combo_TextChanged

AddHandler DropDownlist(i).LostFocus, AddressOf combo_TextChanged2
Else
box6(i).Clear()
End If


Next i
Else
viewable = False
End If
End Sub

To be honest I see people new to programming try this approach and it is a bit off the wall. The average solution to this sort of situation is to create one input screen. Store the entries in a collection and provide forward and backward buttons so you can display/edit any record you like, delete, or add a new record in your single screen.

If you really feel you must visually show all records in a scrollable list.... I would use a DataGridView Control as it can provide a huge list of entries in one go with no custom programming involved. You could use two columns. One for the row title and one for the data.

Using a DGV as Gruff suggested is a good choice, but if you insist on using the TextBoxes and ComboBoxes as you have laid out then I would suggest using a "New Line" button to insert the next line rather than trying to auto-guess what the user wants and adding new lines when you think they are needed. You could even use a NumericUpDown in tandem with the New Line button so users could choose to add multiple lines in one shot. Either way I think guessing and auto creating multiple lines in batches of 20 is a bad idea.