How to get filtered lookup table?

Hi SBGoh 

I don't quite understand what you mean by you want to get 2 tables. If you're trying to get the CS No in Partner wherein the POS # is the max for each POS # and which SO # is equal to the current row in SO # in Sales Order, you can try either of these:

=
CALCULATE (
    MAX ( Partner[CS No.] ),
    FILTER (
        Partner,
        VAR MaxPO =
            CALCULATE ( MAX ( Partner[POS #] ), ALLEXCEPT ( Partner, Partner[SO #] ) )
        RETURN
            Partner[SO No] = EARLIER ( SalesOrder[SO N#] )
                && Partner[POS #] = MaxPO
                && Partner[Code] = "ZC"
    )
)


=
VAR MaxPO =
    CALCULATE (
        MAX ( Partner[POS #] ),
        FILTER ( Partner, Partner[SO #] = EARLIER ( SalesOrder[SO N#] ) )
    )
RETURN
    CALCULATE (
        MAX ( Partner[CS No.] ),
        FILTER (
            Partner,
            Partner[SO No] = EARLIER ( SalesOrder[SO N#] )
                && Partner[POS #] = MaxPO
                && Partner[Code] = "ZC"
        )
    )

 Otherwise, please post a sample data that we can copy-paste (not an image).