Hi Allison,
I have taught a number of advanced Excel courses to engineers, and have yet to find a really comprehensive text or set of teaching materials, so ended up having to create my own. If you find anything really good, would you let me know?
An important factor to consider is how much of the course to devote to VBA. If the engineers are already pretty proficient with the basic features of Excel, perhaps quite a bit should be VBA--which increases the power of Excel substantially in areas that are often of interest to engineers.
I think it is also important to let the engineers know about things that Excel is weak in, such as 3-D and contour plotting, so that they don't waste too much time trying to do in Excel things that would be better done in some other application.
I hope this helps.
Damon