Create a counter action that has an input for the start value and an output for the current value.  Just add one to the value in the action.  Then that will give you an output to check to get your count for your "do the following until".  The reason I am suggesting a separate action is so you have something to use again if needed.

So something like this works, at least it tested ok.  So basically you have a counter to start outside the loop that sets the count to 0 and creates a storage place for the current value.  Then as you see in the Counter input you just add one and store it in the first counter and return it so its passed into the internal counter.  You really do not even need to have the action do anything except have an integer input and an integer output.