I'm new to this. I have created a navigation form with 3 tabs. when I click on one tab it opens a pop-up form where I chose a record from a drop-down. when I click on a command button to "open file" I want the form to open in the tabs 'sub-form window'. at the moment all it does is opens in a separate window.  

how do I get the form to open in the navigation sub-form window where it is linked, with the correct information in the fields based on the combo box?

```
Private Sub Amend_record_Click()
On Error GoTo Err_Amend_record_Click

    Dim stDocName As String
    Dim stLinkCriteria As String

    vFormName = Screen.ActiveForm.Name
    stDocName = "invoice_amend"

    vtest = Me![Combo0]
    stLinkCriteria = "[InvoiceID]=" & Me![Combo0]

    DoCmd.OpenForm stDocName, acNormal, , , acFormEdit, , stLinkCriteria
    Forms![navigation_form]!NavigationButton18.SetFocus

    DoCmd.Close acForm, vFormName

Exit_Amend_record_Click:
    Exit Sub

Err_Amend_record_Click:
    MsgBox Err.Description
    Resume Exit_Amend_record_Click

End Sub

```