Update Query Frustration

I am executing an update query in access as follows....
UPDATE (tPriceSmart INNER JOIN tPriceRaw ON tPriceSmart.IdProd = tPriceRaw.IdProd) INNER JOIN tCusMas ON (tPriceRaw.IdPriceSchd = tCusMas.CM_OVRIDE) AND (tPriceSmart.IdCust = tCusMas.CM_CUSTNO) SET tPriceSmart.AmtOverRide = IIf([DtePrice1]<=CDate(Date()),[AmtPrice1],IIf([DtePrice2]<=CDate(Date()),[AmtPrice2],0))
WHERE (((tPriceRaw.IdPriceType)=8));

Here's my stab at converting this to a stored proc.

UPDATE (tPriceSmart INNER JOIN tPriceRaw ON tPriceSmart.IdProd = tPriceRaw.IdProd) INNER JOIN tCusMas ON (tPriceRaw.IdPriceSchd = tCusMas.CM_OVRIDE) AND (tPriceSmart.IdCust = tCusMas.CM_CUSTNO)
SET tPriceSmart.AmtOverRide =
SELECT
CASE
WHEN DtePrice1 <= GetDate() THEN AmtPrice1
ELSE (CASE WHEN (CASE DtePrice2 WHEN '00/00/0000' THEN '1/1/1900' END) <=GetDate() THEN AmtPrice2 ELSE 0 END)
END
WHERE tPriceRaw.IdPriceType=8

I kknow the Join Statement works becasue it does work in the context of a select. I also know the case logic is working becasue I am using it in an Insert query elsewhere.

Can't quite pull it together though. I am getting an error at Line #1 "(". I gave it a good try though before I resorted to throwing it into the forum. I am sure it is a stupid syntax error. Any help would be appreciated.