Range Lookup for Marketing Attribution

StephenClarke,

Try this calculated column in the Orders table. There is no relationship between these tables in this example.

Marketing Activity = 
VAR vTransactionDate = Orders[Transaction Date]
VAR vClient = Orders[Client]
VAR vMarketingTable =
    FILTER (
        Marketing,
        Marketing[Client] = vClient
            && Marketing[Date of Marketing Activity] < vTransactionDate
            && Marketing[Date of Marketing Activity] >= vTransactionDate - 90
    )
VAR vMaxDateMarketingActivity =
    MAXX ( vMarketingTable, Marketing[Date of Marketing Activity] )
VAR vResult =
    MAXX (
        FILTER (
            vMarketingTable,
            Marketing[Date of Marketing Activity] = vMaxDateMarketingActivity
        ),
        Marketing[Marketing Activity]
    )
RETURN
    IF ( ISBLANK ( vResult ), "NA", vResult )