calling a module in a .asm file into that
of a .c file .
Bear with me, we have a language problem here.
Module: source file
Routine: assembler xxx: ... ret
Function: C foo(){}

Keil assembler modules .a51
Keil C modules .c

Let me try overcome the language barrier another way:
do you want
1) to call an assembler routine from a C function
or
2) do you want to insert lines of assembler in a C module

I am aware you are trying your darndest to express yourself in english, but to give the right answer we need a clear question.

Erik