Try the !callers command. Its a little more complicated than a simple !assist command but also more flexible.

"!callers" shows you all current callers with a link to assist each and make a macro for each. It also lets you assist -all- callers and make a single macro for -all- callers (though that will be limited to 4-6 callers depending on the length of their names).

!callers add [name] <- adds a new caller
!callers del [name] <- deletes a caller