This example sets the size of a form to 75 percent of screen size and centers the form when it's loaded. To try this example, paste the code into the Declarations section of a form, and then press F5 and click the form.
Private Sub Form_Click ()
Width = Screen.Width * .75 ' Set width of form.
Height = Screen.Height * .75 ' Set height of form.
Left = (Screen.Width - Width) / 2 ' Center form horizontally.
Top = (Screen.Height - Height) / 2 ' Center form vertically.
End Sub