With the subs you have listed, sub A will run and close and so will sub B. If you have a UserForm that is called up within sub A, I believe it will still be showing until sub B is done. If your specific issue is having the UserForm disappear, you may want to use an Unload UserForm command just before the Call statement.
The mystery is why you would even write code after the Call B in Sub A. You will probably need to qualify your code within Sub A so that the code knows whether to Call Sub B or to continue with Sub A. You will probably want to do something like this:
If (WHATEVER YOUR CONDITION IS) Then
Call Sub B