get accounting period of last DateModified

[#1]

I need to get the accounting period (Fiscal-Month) of a the last DateModified,I thinking of this, but does not work at all,

I try to lookup the Accounting period of my DIM_DATE where all dates are entered with the correspondig AP:

MAX({<(MAX(DSS_INVENTORY.DATE_MODIFIED))={"=$(=DSS_DATE.DAY_DT)"}>} DSS_DATE.AP)

How can I do this?