exec command using BS x, y, z() produces errors

I'm trying to use the exec function to set a breakpoint which results in a function call. The same BS statement is fine when used outside of an exec call.

Ex:

BS REGNAME,1,functionname() <- works fine

FUNC void somefunction(void)
{
   BS REGNAME,1,functionname() <- "Literal expected" error.
}

Is this a limitation of the software? I don't see any such restrictions listed in the help file for exec.