Hi Listers,
ReturnVisExtent was the riht one!

Thanks a lot

Peter

Original Question was:
Hi Listers,
thought this is an easy one, but

aView = av.getActiveDoc.GetDisplay
y_max = aView.ReturnExtent.GetTop
y_max.SetFormat("dddddddd")
MsgBox.Info(y_max.AsString,"")

does not return the upper y coordinate of the visable extent of the view
(It's around 50 m too less).

Does anybody out there know what's the problem?

Thanks a lot Peter