Fullscreen help

[Doomy]

hello
i need someone to help me with fullscreen

i keep getting an error

that is always highlighted when the error comes up

If frmChars.optFullscreen.Value = True Then

Select Case frmChars.cmbFullscreen.ListIndex
Case 0
If Screen.Width 640 And Screen.Height 480 Then
Call DD.SetDisplayMode("640", "480", ColourDisplay, 0, DDSDM_DEFAULT)
End If
Case 1
If Screen.Width 800 And Screen.Height 600 Then
Call DD.SetDisplayMode("800", "600", ColourDisplay, 0, DDSDM_DEFAULT)
End If
Case 2
If Screen.Width 1024 And Screen.Height 768 Then
Call DD.SetDisplayMode("1024", "768", ColourDisplay, 0, DDSDM_DEFAULT)
End If
Case 3
If Screen.Width 1280 And Screen.Height 1024 Then
Call DD.SetDisplayMode("1280", "768", ColourDisplay, 0, DDSDM_DEFAULT)
End If
End Select

and the error is

Compile Error:
Method or data member not found