Convolution integral

Hi, this is the first time i write in this forum but i work with comsol multiphysics since his name was Femlab, and precisely I use the pde mode apllication to solve nonlinear static and time depending problems. Right now I'm trying to implement a nonlinear time depending problem where I need to use a forcing term that is a convolution integral (in time domain) of the indipendent variables and/or their time derivatives. Does someone know if it's easily possible to do that directly with comsol commands? Maybe I need to modify the code by using comsol script? Or perhaps I definitely may not do that?
Hope someone could give me some good answer
Bye
Andrea