Appologies... I looked at your screen capture by zooming in. The error is simple.
You are connecting the output of the counter and feeding it to "Multiply.vi" by 0.04. The problem is that it is feeding values which are input to a vi "VISA WRT/RC". That is the circular reference which is not allowed. Can you move the vi's that do the calculations inside the loop? That will resolve the problem. I did not see anything preventing you from doing that. Sorry about my first reply... -JLV-
