Word Puzzle

Hello everyone,

I am working on a word puzzle on Storyline 360 and i face a problem with some variables I have added.

I want the user to find the first and the last letter of each word. So I put a Hotspot on the first and the last letter of the word and I create a variable with the name of each word. Every time the user finds the first and the last letter of a word, a trigger adds +1 to the variable and a rectangle shows up highlighting the word in order to show the user that he found the word!

The problem is that if the user clicks on the first letter, then clicks on a wrong letter and then clicks again on the first letter for a second try, the variable sets automatically 2 and the rectangle appears, showing the user the word by mistake.

Is there any way to prevent adding +1 to the variable , every time the user clicks on the hotspot, apart from the first time?

Thanks in advance!