How to call javascript function on image click

[jonambed]

I have a window application where I login in a site which have i login name & password through vb.net
I do all the this to see the name & id of login, password & submit buttonfield from html source.
Now i have problem I have a site where login & password has id & name that i provide frequently. but on submit this is an image & calling javascript fuction so i can not find out id of submit image.
tell how can i find out id of submit & how to pass it in our code.