I can't figure out how to code this.

What I want is for a text box to generate a random number for an account number database field every time i click the new button. The text box will search the db and if it can't find the random number there, it will paste it in the accountnumbertextbox to be saved after clicking a save button.

So far, here's my code.

Code:
Private Sub btnnew_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnnew.Click

        Do Until Not Me.txthiddensearch.Text = AccountNumberTextBox.Text
            Randomize()
            Me.txthiddensearch.Text = (Str(Int(Rnd() * 3)))
            Me.CustomersBindingSource.Filter = "AccountNumber = '" & txthiddensearch.Text & " ' "
        Loop
        Me.CustomersBindingSource.AddNew()
        AccountNumberTextBox.Text = Me.txthiddensearch.Text


    End Sub




    Private Sub btnsave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnsave.Click
        Me.Validate()
        Me.CustomersBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(UsersDataSet)
        Me.txthiddensearch.Clear()
    End Sub
I'll be honest I'm confused with how the loop is supposed to work.