Finding datetime diff by start and min temp value timestamp in groups

Hi,

I would like to have measure that show me the time between timestamps of start measuring value and achieving the minimal value. It works properly on level of ID_key but on the highest level of agreggation I would like to have sum of time of every unit.

This my measure

Czas wychlodzenia TOTAL =
vAR P =min(V_PBI_POMIAR_IB[ROW_KEY])
var tab = cALCULATETABLE(ADDCOLUMNS (
GROUPBY ( V_PBI_POMIAR_IB; V_PBI_POMIAR_IB[ID_KEY];V_PBI_POMIAR_IB[IB] );
"ZAŁADUNKE SL"; CALCULATE (
min( V_PBI_POMIAR_IB[ROW_KEY] );
FILTER ( WMIAR_ZDARZENIE; WMIAR_ZDARZENIE[ID] = 1 )
);
"UZYSKANIE MAKS";
CALCULATE (
MIN ( V_PBI_POMIAR_IB[ROW_KEY] );
FILTER (
ALLEXCEPT(V_PBI_POMIAR_IB;V_PBI_POMIAR_IB[ID_KEY]);
V_PBI_POMIAR_IB[VALUE] = MIN ( V_PBI_POMIAR_IB[VALUE] )
)
);
))
return
sumx(tab;DATEDIFF([ZAŁADUNKE SL];[UZYSKANIE MAKS];HOUR))

Please help me finding solution