Help Find Error

What's wrong with this code??

   In PBCC, I get a compile error # 476 here and yet I don't see the
error. (N , ALF and X are declared global variables in PBMAIN)

 SUB GetSol()
   LOCAL C AS LONG
   FOR C = 1 TO X
      IF X  MOD  C <> 0 THEN GOTO 99
      IF (C*N+C)  MOD ALF <> 0 THEN GOTO 99
      CALL UseThis(C)
      EXIT SUB
99
   NEXT C
END SUB