Suggestions. Experiment with variants of

..Document.Elements("user$btnSubmit").Click()
..Document.getElementsById("user_btnSubmit").Click ()

Try braces too which matches the syntax for some scripting languages
as in:

..Document.Elements["user$btnSubmit"].Click()


Also, look for a form tag as in "<form name='aForm' method=POST

Then try

..Document.Forms("aForm").getElementsById("usr_btn Submit").Click()