I did a lot more experimentation and discovered that ALL of the arguments to the Request function should be variables. The way the manual is worded, I thought that I had to supply some of the values. That's why the example in my first post kept failing.
My line now reads like this:
ParmNum = REQUEST ("ASSOCLP_PARVALUE" ,"Frame_Type", Var1, Var2, Var3, Var4, Var5, ParmValue)
I'm not using any of the intermediate arguments, only ParmValue, so the variable names are lame.
Thanks for your help!