This is what I would like to accomplish and I hope that someone has done something similar before.
I have a password field that I want to initially show the default "guest" password. ie. "Guest", but not "*****".
Then, when a user clicks on the field, the text they type should be displayed as "*****" not "mypass" etc.
Get it? I think the only way may be via substituting two different fields, but I would rather avoid that if possible.