Use WaitForSingleObject winapi function to wait till the browser window is closed. Check the following links for the same:
How to wait for a shell process to finish before executing further code in VB6
http://www.ex-designz.net/apidetail.asp?api_id=539
http://us.generation-nt.com/answer/how-start-notepad-modal-dialog-vb-application-help-54054422.html