Access VBA Merge Glitch

[dukquack]

Hey Guys,

I found this code somewhere on the internet, maybe even from this forum but I can't remember, basically, the merge works great but the issue im having is, when the merge is open and, lets say the user closes the word document, but then needs it open again, so they re-click the button on the form that activates the merge again, it gives an error, below is the code:

Option Compare Database

Dim WithEvents oApp As Word.Application

Private Sub Command0_Click()

    Dim oMainDoc As Word.Document
    Dim oSel As Word.Selection
    Dim sDBPath As String

    Set oMainDoc = oApp.Documents.Open("U:\test")
oApp.Visible = True

    With oMainDoc.MailMerge

        .MainDocumentType = wdFormLetters

        sDBPath = "U:\Letter Database.mdb"
        .OpenDataSource Name:=sDBPath, _
           SQLStatement:="SELECT * FROM [tblcompanies]"

    End With

    With oMainDoc
        .MailMerge.Destination = wdSendToNewDocument
        .MailMerge.Execute
    End With

    oApp.Activate
    oApp.Documents.Parent.Visible = True
    oApp.Application.WindowState = 1
    oApp.ActiveWindow.WindowState = 1
    
End Sub

Private Sub Form_Load()

Set oApp = CreateObject("Word.Application")

End Sub

Private Sub Form_Unload(Cancel As Integer)

Set oApp = Nothing

End Sub

The error I am getting is:

"Run Time Error '91':
Object Variable or With Block Variable Not Set"

And debug is highlighting this code:
Set oMainDoc = oApp.Documents.Open("U:\test")

I am using access 2007, any help would be appreciated as I am a novice with vba.

Thank you!