So currently i am trying to programm a game. for that i would need a Textbox that is updating once the player makes an input. I have a textbox TB1 and a button with the action linked. the action that the button should make is calling an external procedure which in turn updates the textbox. But i currently i keep getting the following error expresion:

Error, (in Maplets:-Tools:-Set) invalid argument(s): [TB1]::string = [7, 8, 9]

So what die i do wrong.