Is there a way to change the size of the default MsgBox() and the size of the
buttons?
No.
You can create your own unbound form to use as a message box.
You can size the buttons any way you like.
Add a command button to the form.
Code it's Click event:
Me.Visible = False
You call the message form using something like this:
Dim strMessage as String
strMessage = "this is your message"
DoCmd.OpenForm "MessageFormName", , , , ,acDialog, strMessage
' You can do additional stuff here.
DoCmd.Close acForm, "MessageFormName"
Code the Form's Load event:
If Not IsNull(Me.OpenArgs) Then
LabelOnForm.Caption = Me.OpenArgs
End If
The form will display your message until you click the command button
to hide the message. Then the code will continue and close the form.