QuarkXPress 7.0x: how to script a "and-clause" for a search&replace?


I am trying to search every hard return and replace them by soft ones - but: only if the character font is e.g. “Helvetica” and size e.g. 12. I don’t get the right references, the second clause doesn’t work. Has anyone a hint? Would it be better to reference “text range”, story, text …?
Thanks for reading.

So far:

set searchStr to (ASCII character of 13)
set replaceStr to (ASCII character of 7)
		tell docRef
			set TheStories to count of every story
			repeat with i from 1 to TheStories
					set mysearch to (a reference to (text of story i whose contents of it = (searchStr)))
				       -- and (text of story i whose font of it = (myFont))))
					--set searchReferences to ((object reference of every text style range of every story) whose font is theFont) 
				end try
				set contents of mysearch to (replaceStr)
			end repeat
		end tell