I'm not sure you want a "login" screen. Part of the beauty of QV is the silent single sign-on straight out of the box. Look into restricting access to the application with either (or both) NTFS file permissions and Section Access. Then maybe have conditional shows on different sheets using OSUser(), or another field e.g. UserType if you have one.
Hope this helps,
You can use this code
before the scripting of your application
load * inline
After that load your application
load * inline [
After that go to the tab Document properties-Opening-click on the checkbox on Reduction on base of section access.
For further information
Hope this will help you.