Con la siguiente macro, puede devolver el tamaño de la pantalla con la función GetSystemMetrics32.

Declare Function GetSystemMetrics32 Lib "User32" _

Alias "GetSystemMetrics" (ByVal nIndex As Long) As Long

Sub DisplayMonitorInfo()

Dim w As Long, h As Long

w = GetSystemMetrics32(0) ' width in points

h = GetSystemMetrics32(1) ' height in points

MsgBox Format(w, "#,##0") & " x " & Format(h, "#,##0"), _

vbInformation, "Monitor Size (width x height)"

End Sub

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