SAP BEx Query data tracking using RefValue

Hi All,

I selected data tracking for MTD Invoice $ (This measure is coming from BEx Query) and created another variable in WebI Prior Day Change which is "=RefValue([Invoice $])

My data tracking seeting is compare data refresh from....today is Nov 18th and the compare option default shows Nov 18th and the Invoice $ and the Ref Value is all the same.

I was expected to see Ref value with Nov 17th data.

Any suggestion...