So you need to change the loop to only look for particular text CCs. I would do this by using the CC Title property to nominate which text CCs are meant to feed the XL workbooks
Code:
Function UpdateXL(xlWkBk As Object)
Dim aCC As ContentControl, sSheet As String, sCell As String, sValue As String
For Each aCC In ActiveDocument.SelectContentControlsByTitle("Excel Data")
If aCC.Type = wdContentControlText Then
sSheet = Split(aCC.Tag, "!")(0)
sCell = Split(aCC.Tag, "!")(1)
sValue = aCC.Range.Text
xlWkBk.Sheets(sSheet).Range(sCell).Value = sValue
End If
Next aCC
End Function