Help with a simple beginners program

[knicksfan426]

I've created a program with 2 textboxes and a button. The user must enter a value in each textbox. When the button is clicked, a message box pops up showing the sum of the values entered in each textbox.

Here's the code:

Dim start As Integer
Dim endnumber As Integer
        
        start = TextBox1.Text
        endnumber = TextBox2.Text

       If start > 0 And endnumber > 0 Then
            Dim answer As Integer
            answer = start + endnumber    'Answer becomes the integer in textbox1 + the integer in textbox2
            MsgBox(answer)  'Message box pops up and displays the answer(the sum of textbox1 and textbox2)
        End If

Here's what i want to add: if both or only one of the textboxes have no value entered in them, i want a message box to pop up and say "Please enter a value." I've tried using the do while statement and also used if statements but i kept getting errors. Can anybody help me out here?

Thanks