problem in parameter passing

hi
I am facing a problem in parameters retrieval. I call a function of assembly from C.I pass a struct pointer in the parameter.I am using the Small model.
Parameter are stored at the fixed memory location which is ?functionname?BYTE how can i use this parameters in assembly.
I want to initalize the DPTR with the function pointer passed in the parameter.
if i use instruction
mov DPL,R2
mov DPH,R1
then this is not working i also uses these instruction
mov DPTR,?functioname?BYTE
this generate a syntax error.
Your kind help will be most appreciable.

regards
Farhan Arshad