Hi there,
  I'm pretty new to VBA and have a question. I have a textbox which whenever it is changed, I need a checkbox to be checked unless another checkbox is checked.

Textbox (ISBN)
Checkbox to be changed (Changed) unless another checkbox is already checked (New)

Can anyone help explain it to a new guy?

Thanks,
Arholly

Set up an "After Update" event in the text box properties to [Event Procedure], and click the ... button. The code you want in the procedure would be something like this, with the correct names subbed in:

If me.chkNew = False Then
me.chkUpdate = True
End If