extruded cut on curved surface?

i'm trying to create a 3D model of a device for my internship but i can't create a correct cut. the surface i need to apply the cut on is displayed below. i think i need a plane attached to the surface but i don't know how to create it. do you guys have any idea? thanx!

You need to create a point on the surface, I'd use a 3d sketch to create the point on the surface. A point should automatically attach to the surface with a coincedent mate. Once you have the point on the surface, then you can create a plane at the point and tangent to the surface.

One more thing, remember you cut solids and you trim surfaces. It looks like you have a solid here, so I guess you'll be cutting.

Attached is a quick solid part with a cut through it. I did it by creating a plane above the part with a sketch and a cut through all. The plane could be also put at an angle but for speed I made parrallel.

In this example I suppressed the first cut. Then created a surface parrallel to the curved surface by selecting a scetched point on the upper surface.

thanks for the help. here at my intern company I'm working on SW2005 and I guess you (patycoop) created the examples in 2006. I'll try to open them at home 'cause there I do have that version. bcampbell I probably didn't understand your solution fully because when I follow your directions I can only create a horizontal pane, not a curved one. thanks anyway.