So, looking at that, I'm guessing you're expecting the event to trigger once you enter "40" into the text box? But it doesn't.
Does [ENTER] cause it to exit the field? Maybe try [TAB] instead?
But the easiest thing would be to ask the developers what activates the event trigger.
(The action after entering "40" seems to be clicking an exit button of some sort? Are you allowing enough time for the event to happen before you click this exit button?)
I just noticed, you're using SetText to set the value. Maybe try using Keys instead. I think SetText is like changing a property of the control. Keys is like the user actually keying things in. I've had occasions where SetText appered to work, but the value was not retained. Using Keys, it was fine.