urgent !! add/remove data in listboxes

Hi,
First I want to appologize for my bad English,I hope someone will understand me.
I'm creating a new appliction for my company but I'm stuck.
Here is my problem.
So I created a form with a listbox(1) within data based on a table. Then I created another listbox(2) because I have to select several things from listbox(1). So I placed a button on my form and I can add my selected data into listbox(2).
But I also placed a button on it to remove data from listbox(2) in case of I added something wrong. This also works but when I now want to add new data,he also add the data I already removed. And then second thing I want to use the data of listbox(2) as criteria for a query. It works when I use a combobox but not with a listbox. I already know that I have to work with SQL but I never worked with SQL.
By th way I work with Access97
So can someone help me please??
This is my code

Option Compare Database

Option Explicit

Private Sub Command10_Click()
On Error GoTo Err_Command10_Click

DoCmd.Quit

Exit_Command10_Click:
Exit Sub

Err_Command10_Click:
MsgBox Err.Description
Resume Exit_Command10_Click

End Sub

Sub cmdCopyItem_Click()

End Sub

Function CopySelected(frm As Form) As Integer

End Function

Private Sub Command50_Click() 'add

Dim ctlSource As Control
Dim ctlDest As Control
Static strItems As String
Dim intCurrentRow As Integer

Set ctlSource = lst_bts
Set ctlDest = lst_selectedbts

For intCurrentRow = 0 To ctlSource.ListCount - 1

If ctlSource.Selected(intCurrentRow) Then
strItems = strItems & ctlSource.Column(0, intCurrentRow) & ";"
End If
Next intCurrentRow

' Reset destination control's RowSource property.
ctlDest.RowSource = ""
ctlDest.RowSource = strItems
lst_selectedbts.RowSource = strItems
lst_selectedbts.Requery
txtSelected_bts.Value = strItems

End Sub

Private Sub Command51_Click() 'remove

Dim ctlDest As Control
Dim intCurrentRow As Integer
Dim strItems As String

Set ctlDest = lst_selectedbts

For intCurrentRow = 0 To ctlDest.ListCount - 1

If Not ctlDest.Selected(intCurrentRow) Then
strItems = strItems & ctlDest.Column(0, intCurrentRow) & ";"
End If

Next intCurrentRow
ctlDest.RowSource = ""
ctlDest.RowSource = strItems

End Sub

Private Sub Form_Click()

ReDim strSelectie(lst_bts.ListCount - 1)
txtSelected_bts = ""
End Sub

Private Sub Form_Load()

ReDim strSelectie(lst_bts.ListCount - 1)
End Sub