Check a Field value from another form field.
I have a problem, i am make a form which is like a registration form user registered itself on it, and i am also make a another form for asking question. i want that only registered user can ask his question to me by form. means in both form the "email ID" and "user name" is common field. how can i do that only registered users can ask their questions. means in this form when user type his USERNAME then the field check the data from registration Form and same as check Email ID from registration form and then users can ask their questions. please give me some suitable answer Thanks in Advance