Userform: Textbox Live Clock and Command Button issue

If code is running in one workbook, we are not allowed to do some work in another workbook? Is it the case?

I think it is not clock issue, as long as a userform (even without clock) is openning, the VB developer window shows code running, and I am not able to do anything in other workbooks.

Is it true? How to go around the issue?

Thanks.

Property ShowModal=False

Finally, figure out