toggle to turn full screen mode on and off via onkey shortcut

I have the following code:

If DisplayFullScreen = False Then
    Application.DisplayFullScreen = True
ElseIf DisplayFullScreen = True Then
    Application.DisplayFullScreen = False
End If

which is linked to a key-board shortcut and attempts to turn full-screen mode on or off. The on portion works, but the off does not......... I do not think excel recognizes this if statement:

ElseIf DisplayFullScreen = True Then

Any ideas on how to fix it?

Thank you.