Pivot commandtext change error

[Job]

The error is application-defined or object-defined error. Not sure why this
doesn't work. I can get the ptc.Connection to change, but not the .SQL
statement. Any help is appreciated.

Cheers

Sub ChangeSource()
'Declare our variables.
Dim ptc As PivotCache, oldSrv, newSrv,oldSQL ,newSQL As String

sFilename = Application.GetOpenFilename(, , "Input the name of the
new server or file path which you want the Pivot Table to point to.")
'They have cancelled.
If sFilename = "False" Then Exit Sub
newSrv = "ODBC;DSN=MS Access Database;DBQ=" & sFilename & ";DefaultDir=" &
sFilename & ";DriverId=25;FIL=MS Access;MaxBufferSize=2048;PageTimeout=5;"

For Each ws In ActiveWorkbook.Worksheets
For Each pt In ws.PivotTables
oldSrv = pt.PivotCache.Connection

'Replace the ODBC information of whatever PivotTable
'is currently active.
Set ptc = pt.PivotCache
oldSQL = Left(Mid(ptc.Sql, Application.Find("`", ptc.Sql) + 1, 255),
Application.Find("`", Mid(ptc.Sql, Application.Find("`", ptc.Sql) + 1,
255)) - 1)
newSQL = Application.Substitute(ptc.Sql, oldSQL, sFilename)
ptc.Connection = Application.Substitute(ptc.Connection, oldSrv, newSrv)
' ====> This is error line
ptc.Sql = Application.Substitute(ptc.Sql, ptc.Sql, newSQL)
'====>
Next pt
Next ws
End Sub