Refine Query

Maybe someone could save me some time
Im trying to learn as I go and reached a sticking point that I'm
having a problem finding a direct answer to on the web
I want to refine a query and update a record (or records if possable)
Notes are in the following code
Thanks For your help

Code:

---


    Private Sub Form4_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
     

        Do



            Me.Show()
            Me.Activate()
            Dim BARCODE As String = InputBox("Enter Equipment Barcode")
            'storing the text entered in a string
            If BARCODE <> "" Then

               
                'Load the Record into my form

                'I Want To only Get a Record if the RETURNDATE Colum is blank


              'My fillby query is Select F1,F2...Ect FROM SignedOutEquipment
                '                    WHERE (BARCODE=@BARCODE)
                '                  And Works Fine



                Try
                    Me.SignedOutEquipmentTableAdapter.FillBy(Me.SignoutDataSet.SignedOutEquipment, BARCODE)
                    If Me.SignoutDataSet.SignedOutEquipment.Rows.Count = 0 Then
                        MsgBox("That Item Was Not Signed Out", MsgBoxStyle.Critical, "Barcode Not Signed OUT")
                        Me.Close()
                    End If
                    'Here I insert todays date into the form
                    Dim now As Date = Date.Now
                    now.ToString("F")
                    RETURNDATE.Text = now


                  'Now I want to Update the record with the RETURNDATE Field
                    'and save it back to the Database

                Catch ex As System.Exception
                    System.Windows.Forms.MessageBox.Show(ex.Message)


                End Try

             

            Else : Me.Close()
                Exit Do
            End If

        Loop
    End Sub

---

WHERE RETURNDATE IS NULL --Assuming it is actually Null/Blank and not ''