How to "do" this

[Björnke von Gierke]

I want to loop over each object where as the object can be specified by 
the user is there a way to get this working? The problem is that the 
repeat loop does not understand this part, which should evaluate to 
"Fields":  (theO & "s")

on mouseDown
   --Button "Object" = Field
   put the label of Button "Object" into theO
   --button "stack name" = the name of a open stack
   put the label of button "Stack name" into theS
   repeat with x = 1 to the number of (theO && "s") in stack theS
     do "put" && theO && x && "of stack" && quote & theS & quote && "& 
return after me"
   end repeat
end mouseDown