Is there a way to tell CAS that a variable is a constant?

[webmasterpdx]

I can use assume to specify that a variable is an integer or >0 etc, etc....but is there a way to tell the cas system that a variable is a constant?
I've been having problems with the integration system and most of these problems would be easier for the system to resolve if it knew that certain variables were constants....something like assume(a,constant) (which doesn't work)....

Any ideas?
Thanks in advance
-Donald