If you really have the leading and ending square brackets, I would say that's the problem. If not, the message is telling you that the name of the control you're clicking on to run this event doesn't match the name as it is defined in the procedure - cmd3_Click. Perhaps you changed the name of the control.
Such names are not much help in identifying what's what down the road. You should adopt a naming convention. Welcome to the forum by the way. If you would be so kind, please use code tags for anything more than a few lines. It's the # on the message toolbar.
Thanks.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.