VGetButtonLabel - returns the label of a Button Item.
  VGetButtonLabel(ID, val)
  char *val;                            /*RETURN*/
  VGetButtonLabel returns the label of a given Button Item.
  typedef struct _button {
        Window  win;            /*window in which item resides*/
        short   type;           /*type of button(0=button, 1=toggle, etc..)*/
        short   x,y;            /*location of upper-left corner of item*/
        short   w;              /*width of the item area in fonts*/
        short   h;              /*height of the item area in fonts*/
        short   label_width;    /*width of label in pixels*/
        short   label_height;   /*height of label*/
        short   label_ascent;   /*ascent dimension of font*/
        short   label_x;        /*position of the label*/
        short   label_y;
        short   thick;          /*thickness of frame*/
        short   width;          /*width of item in pixels*/
        short   height;         /*height of item in pixels*/
        int     fw,fh;          /*size of font*/
        char    label[150];     /*label of the button item*/
        short   state;          /*indicates if button item is OFF(0) / ON(1)*/
        short   mode;           /*0=RELEASED, 1=PRESSED*/
        int     (*func)();      /*notify procedure*/
        struct _button *next;   /*next button item*/
Return Value
  0 - work successfully.
  266 - invalid Button Item ID.
  269 - no Button Item found.
  271 - Button Item value is NULL.
  ID - ID of the given Button Item.
  val - character string in which label is returned; should not be NULL.
Side Effects
Entry Conditions
  VAddButton should be called first.
Related Functions
VAddButton, VSetButtonLabel.