Here is your problem. The line of code that you quote above is in TxtFollowUp1_Change. This Sub is executed whenever the content of TxtFollowUp1 changes. As soon as that happens, you are replacing its contents with whatever is in TxtCallDetail. So the moment that the user types one character into TxtFollowUp1, it is replaced by whatever is in TxtCallDetail. Therefore you will never be able to type anything into TxtFollowUp1.

Because I don't know what you intend to do here, I can't fix it for you. If you describe the behavior you want I can help further. My wild guess would be that this should be renamed Sub TxtCallDetail_Change.