Hi,
I was experimenting with Mask.
I didn't quite understand it, but it seems to work better the following way (in case it's useful). (DEST_IN, DEST_OUT)

Code:
'        nFinalCheeseC.Operator = iOperator
'        nFinalCheeseC.MaskSurface nMask, 0, 0  ' Apply mask
'        nFinalCheeseC.RenderSurfaceContent nShouldHaveHoles, 0, 0  ' Draw the main image where the mask allows
    
        nFinalCheeseC.Operator = iOperator
        nFinalCheeseC.SetSourceSurface nShouldHaveHoles
        nFinalCheeseC.MaskSurface nMask, 0, 0  ' Apply mask