Trimming the surfaces

I need to trim two plano surfaces and can't find example in API Help how to do that. Trying to do something like that:

boolstatus = myModel.FeatureManager.PreTrimSurface(

False, True, False, False)

boolstatus = myModel.Extension.SelectByID2(surfacename1,

"SURFACEBODY", 0, 0, 0, True, 0, Nothing, 0)

boolstatus = myModel.Extension.SelectByID2(surfacename2,

"SURFACEBODY", 0, 0, 0, True, 0, Nothing, 0)

myFeature = CType(cl.myModel.FeatureManager.PostTrimSurface(False), Feature)

and have myFeature = Nothing.

Any suggestions?

Thanks for help,

Simon

SolidworksApi macros