VB2010: Actions on Click?

Hey People,

Me again, im moving on to different programs now.

Could someone assist me in advising me how to make buttons in VB2010 work so that if i click them it fills a login box.

So on click it would fill:

Username: testuser1
PAssword: password1
Domain: testdomain

And it would then optionally hit the Enter.

I know its possible just cant think of how at the moment.

Help Please.