OK, so in the interim of 1 of you gurus explaining the proper way, I kept on trucking, and eventually came up w/ this (attached).
I cut a thru slotted hole in the base part. Then, I made a new sketch on the plane which is the bottom surface of the base part - that sketch was basically a "convert entities" where I converted the slot sketch which was used to cut the hole. I also offset a smaller concentric slot onto a plane a specified distance above the top surface of the base part.
Then, I lofted from the sketch on the bottom surface of the base part, to the offset plane sketch. Then, I shelled this out.
What that did was it made it look like the feature (ie, in this case, rubber) was attached from the bottom surface to the top edge of the offset slot. (what I'm talking about can be seen in the attachment easier than trying to explain in words).
This might not be the "proper" way, and I'm sure it can't be manufactured, but for now, until someone chimes in w/ some assistance in the proper technique - I'm going to move on to the next things I'm trying to do.
I just wanted to post this in case anyone was having similar issues, and in the hopes it can spur some ideas!!
Thanks in advance,
Just to update this, as perhaps I didn't fully explain...
I have approximated what I want by using the Loft technique, as shown above. However, if this were to be manufactured, I'm pretty sure that technique wouldn't suffice.
The material between the button & the lid is made of rubber, whereas the button & the lid are obviously hard plastic. The elasticity of the rubber allows the button to be depressed, and that's what I'm not sure of how to accurately model - both the "natural" (undepressed) state before someone presses the button, and then the "wrinkled" (depressed) state after the button is pressed - obviously, the rubber will bend & distort to allow for that motion.
I would probably model it the same as Rob S. did, followed by a Thicken command. You won't really be able to model the way that the real rubber folds, but it will probably be close enough. If you really need to know how the rubber will distort, then you would have to run a non-linear hyper-elastic material analysis with the correct material properties. This will be a royal pain, first to get the material properties and second to get the analysis to run.
The rubber itself will be fairly thin, say .010" for a typical button. You would probably need to have a fairly large contact pad where the rubber bonds to the plastic on both sides, probably the full side of the surround and the full bottom.of the button .