Inserting Asp.net UserID into web form.

I am trying to capture the UserID from Asp.net Login structure and then insert that value into a form so it captures the UserID in another record. I have confirmed that the stored procedure behind the form works and inserts information. I just cannot capture the UserID and insert that value in the form. I have this code in the code behind page,

Public Sub New()         Dim memUser As MembershipUser         m ...