Windows application-During the Runtime it is looking for window to be activated how can i do that?

In addition to baxatob's questions, it might be interesting to see the code that you're using to do the entry into the login fields.  Generally the "Keys" command should work for entering data.  If necessary, you can even add a "[Tab]" character or command to the end of the Keys parameter to simulate "leaving" the field... a typical thing to have an "OnExit" event fire before activating buttons on a login form.  But it would be nice to see what you have first before we start making a lot of suggestions.