VChangePanelItem - changes the panel command name for the specified command.
  VChangePanelItem(old_cmd, new_cmd, switch_item)
  char *old_cmd, *new_cmd;
  int switch_item;
  VChangePanelItem changes the panel command name for the specified command
item. If the specified panel item is a switch, VChangePanelItem updates the
command and the switch value. If it is a button, VChangePanelItem updates 
the command only. If the whole command field is greater than MAX_PANEL_CHARS, 
then VChangePanelItem displays only MAX_PANEL_CHARS and truncates the rest of 
the command field.
Return Value
  0 - work successfully.
  216 - panel is not displayed in the dialog window.
  253 - invalid panel command type.
  254 - panel command has been truncated.
  255 - the specified panel item cannot be found.
  258 - pixmap is NULL and image window is at the front.
  old_cmd - the old command to be changed.
  new_cmd - the command name to be changed to.
  switch_item - the value of switch item to be displayed.
Side Effects
Entry Conditions
  If switch_item is invalid, old_cmd or new_cmd is NULL, or VCreateColormap
is not called earlier, VChangePanelItem prints an error message to the
standard error stream, produces a core dump file and exits from the current
Related Functions
VDisplayPanel, VErasePanel, VGetPanelInformation, VSelectPanelItem.