Open Report On A Form With A Button

Good morning All,
I have a form with a command button to open a report ( based on a query ) for the currently displayed record. here is the code I have used:

Private Sub CS_notes_Click()
On Error GoTo Err_CS_notes_Click
Dim stDocName As String

stDocName = "InternalSNwithRMAprodMASData"
DoCmd.OpenReport stDocName, acPreview, , "TLAUnit = " & Me.UnitSN & "'"

Exit_CS_notes_Click:
Exit Sub

Err_CS_notes_Click:
MsgBox Err.Description
Resume Exit_CS_notes_Click

End Sub

I believe this came from this forum sometime. When the button is clicked I receive the error:
"Syntax error (missing operator) in query expression '(TLAUnit = 26712B')'

TLAUnit is the report field, UnitSN is the form field.
Any help with the error?
Thanks
Kevin