How can i define UDFs for void functions ?

I get an error for this syntax:
"DECLARE EXTERNAL FUNCTION OUTPUTDEBUGSTRING Cstring(64)
ENTRY_POINT 'OutPutDebugString' MODULE_NAME 'kernel32.dll';"

More specifically, how can i define UDF for OutPutDebugString api
function in kernel32.dll?

I want to use it in Stored Procedures.

Thanks.