Using Hidden Field to Collect User Input in Access Form

Using Visual Basic with an Access database.
I created a form to copy existing product specifications from an existing product number to a new product number.

We need to collect the source # from the user (as Snumber), copy those specs into two temporary tables, then get the target # from the user (as Tnumber) and copy the specs from the temporary tables and append them to the permanent tables, changing only the Product # to be equal to Tnumber.

Here's the code in the Open Event in which I get a compile error at "Me.HiddenField = Snumber".
The error reads:  "Method or data member not found".

I'm no expert at writing VB code so I'm sure there is a statement missing or some missing global declaration?

Private Sub Form_Open(Cancel As Integer)
    Dim Snumber As String
    Dim Tnumber As String
    Snumber = InputBox("Source Product# ?")
    Me.HiddenField = Snumber
    DoCmd.OpenQuery "qryQCPH"
    DoCmd.OpenQuery "qryQCPT"
    Tnumber = InputBox("Target Product# ?")
    Me.HiddenField = Tnumber
    DoCmd.OpenQuery "qryQCPH2"
    DoCmd.OpenQuery "qryQCPT2"
    DoCmd.OpenQuery "qryQCPHappend"
    DoCmd.OpenQuery "qryQCPTappend"
    DoCmd.SetWarnings True
    Cancel = True
End Sub