Xaw question

[a]

(If you know other list I should post, please tell me.) 
why does my scrollbar not scroll?

Please reply to [EMAIL PROTECTED], i'll leave in a minute.

#include  <X11/Intrinsic.h>
#include  <X11/StringDefs.h>
#include  <X11/Xaw/Form.h>
#include  <X11/Xaw/Scrollbar.h>
#include <stdio.h>

float gg=0.0;

void scroll(Widget w, XtPointer client, XtPointer call)
 {gg+=0.1;
  XawScrollbarSetThumb(w,gg,gg); printf("%d %f\n",(int)call,gg);
}

main(int argc,char **argv)
 {Widget toplevel,form,entry; XtAppContext appcon;
  int n,i; Arg wargs[10];

  XtSetLanguageProc(NULL, NULL, NULL);
  toplevel=XtAppInitialize(&appcon,"xzip",NULL,0,&argc,argv,NULL,NULL,0);

  XtSetArg(wargs[0], XtNdefaultDistance,0); 
  form=XtCreateManagedWidget("sb", formWidgetClass,toplevel,wargs,1);

 XtSetArg(wargs[1], XtNlength, 100);
 XtSetArg(wargs[0], XtNorientation, XtorientVertical);
 entry=XtCreateManagedWidget("g", scrollbarWidgetClass,form,wargs,2);
 XtAddCallback(entry,XtNscrollProc,scroll,NULL);
 XtRealizeWidget(toplevel); XtAppMainLoop(appcon);

}