Yes indeed, this works:
extern void WINAPIV VCOMP__vcomp_fork(DWORD parallel, int ncount, void (__cdecl *helper)(__ms_va_list), ...); __ASM_GLOBAL_FUNC( VCOMP__vcomp_fork, "pop %eax\n\t" /* save return address */ "add $8,%esp\n\t" /* skip parallel and ncount */ "pop %ebx\n\t" /* save helper */ "push %eax\n\t" /* set up return address */ "jmp %ebx" /* enter handler */ )