Mike Gage just gave a talk on WeBWorK at HKUST and for that he created 3 demo courses which illustrate many of the problem techniques that can be used. For example using flash applets (your previous post) and sequential problems which may be relevant to your current post. Take a look at
https://hosted2.webwork.rochester.edu/webwork2/HKUST101
and also HKUST102 and HKUST103. Login instructions on on the first page.
Arnie