Is it possible for the msgbox to pop up in the centre ??? Can i use MessageDialog to do this??? Or do i need to make a custom window to do this??
No.
Not with standard tools.
Yes.
If you are not already familiar, here is the code to center a window (placed in the open event) on OSX.
Soft Declare Sub center Lib "Cocoa" selector "center" (windowRef As Integer)
center(self.Handle)