Hello cplindem,

By default, UserForms are displayed modally. A modal form disables input to it's owner window (in this case Excel) and the owner's child windows until the UserForm is dismissed.

However, you can change the modallity of the UserForm either by changing the ShowModal property in the Properties Window to False or explicit setting the Show method Modal argument to False at run-time.

Example of Changing the UserForm's Modality at Run-time
    UserForm2.Show Modal:=False