Hi,
My Add-In I am opening a user form displayed as modal dialog on clicking a
toolbar button.
From this form, on a button click, I am opening 'GetSaveAsFileName' dialog
to get the file name from user.
After dismissing the dialog, the userform becomes inactive and I am able to
select cells on the active worksheet.
Is this a known issue with Microsoft?
Is there any solution to activate my form and restrict the user from
accessing worksheet.

Regarding restricting access to worksheet, I am able to restrict the user
access by setting the application.interactive property to false.
But with this setting, I am not able to display the userform if I select
multiple sheets before displaying the dialog. I am getting the following
error.

Runtime error 1004,
Method 'Interactive' of object '_Application' failed.

Advance Thanks for help
-Ramana