User Picker Field to a Text Field

What are you trying to accomplish, exactly?

One way I've done something sorta like this in the past, when I need to allow a current user to be picked or a new username to be typed, is to have a radio button underneath the User field with choices like {"Existing User", "New Username"}, with "Existing User" selected by default; and if the radio button is changed to "New Username" for example, the form will hide the user picker and show a text field in its place.  Of course this all depends on your implementation and what exactly you're thinking of trying to do.

hey mike,

Thanks for the quick repsonse.

i have done something similar like have given a link underneath which says create user which changes it to a text field and the viceversa. but the requirement was to change the picker field to a text field dynamically  if no results found 

Oh I see - well that's not really feasible because there's no way to tell if "no results found" - the user picker would just not perform any save if no results are found, and as far as the form's concerned the data would then be exactly the same as it was originally - and therefore there would be nothing on which to base dynamically switching the available field.