q pos 
 After this command is issued, GrADS waits for user's mouse click, then returns 
  the coordinates of the mouse click plus additional information. If the nowait 
  argument is used, then GrADS will query the mouse without waiting for a mouse 
  click. The returned information makes 'q pos' such a powerful command 
  especialy when used in conjunction with the different 'classes' of widgets: 
  buttons, rubber bands, and dropmenus. Here is a template of the information 
  that 'q pos' returns after a mouse click (note the difference in 
  output between the different widget classes): 
 Position = xpos ypos mbtn class                                    
  (somewhere in the graphics window) 
Position = xpos ypos mbtn class widget# btnstate                   (for buttons) 
Position = xpos ypos mbtn class widget# xpos2 ypos2                (for rbands) 
Position = xpos ypos mbtn class widget# menuitem <casc# cascitem>  (for dropmenus) 
where:
xpos, ypos    
- coordinates of the mouse click in real page units mbtn          
- either 1, 2, or 3 for the left, center, or right mouse button class         
- either 1, 2, 3, or 0 for button, rband, dropmenu, or 'not a widget' widget#       
- the number assigned to the widget when it was originally set up btnstate      
- either 0 (meaning "off") or 1 (meaning "on") xpos2, ypos2  
- coordinates of the mouse release point in virtual page units menuitem      
- the item number selected from the menu list casc#         
- the cascade menu number selected from the dropmenu list cascitem      
- the item number selected from the cascade menu 
class will be 0 and there will be no further
output.
widget# and menuitem
will both be -1.
casc# and cascitem will
repeat up to three times in the output from 'q pos'. 
set button draw button redraw button set rband set dropmenu draw dropmenu
See the section of the User's Guide on widgets for plenty of script examples showing how to use 'q pos'.