Podrías usar algo como esto:
Código vb:
Ver originalPrivate Declare Function PaintRgn Lib "gdi32" (ByVal hdc As Long, ByVal hRgn As Long) As Long
Private Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Código vb:
Ver originalDim hRgn As Long
Me.AutoRedraw = True
Me.FillStyle = vbSolid
Me.FillColor = vbBlue
hRgn = CreateRectRgn(1, 1, 100, 100)
PaintRgn Me.hdc, hRgn