Upon matching attribute value, increment output

	If I have the following XML:
	 
	<GRP>
	  <CON @CODE="ABC"/>
	  <CON @CODE="DEF"/>
	  <CON @CODE="ABC"/>
	  <CON @CODE="ABC"/>
	  <CON @CODE="XYZ"/>
	  <CON @CODE="ABC"/>
	</GRP>
	 
	And I want my output to be:
	 
	ABC
	DEF
	ABC_1
	ABC_2
	XYZ
	ABC_3
	 
	How would I get there?  I cannot seem to manage it with any combination of count, value-of, match, etc., and almost all posts I see are for node values instead of attributes, or HTML instead of text...nothing I've seen seems to give me a valid idea to run with.
	 
	Any help would be greatly appreciated!
	 
	Thanks,
	 
	Russ