Produce Report Using Wherecondition

I'm trying to print a report that displays only records from a particular site.

This is the code I've used:

Private Sub cmdReport_Click()
On Error GoTo Err_cmdReport_Click

Dim stDocName, strSiteName, stLinkCriteria As String

stDocName = "rptExtChkSht"
strSiteName = Me!cmbSiteName
stLinkCriteria = "[SiteName]=" & "'" & strSiteName & "'"

DoCmd.OpenReport stDocName, acPreview, , stLinkCriteria

Exit_cmdReport_Click:
Exit Sub

Err_cmdReport_Click:
MsgBox Err.Description
Resume Exit_cmdReport_Click

End Sub

I'm wondering whether it won't produce only these records because of the design of my report (attached), with the Site Name under the SiteID Header...?? I wouldn't have thought it would matter, but...

Any help greatly appreciated.