Query field string too long

[DataMiner]

Let's say I have a query like:

select [x]+[y] as A, [z]*[A] as B from MyTable.

I have found that sometimes this works and sometimes it doesn't, (Like, it works the first time I run it, but later quits working....)so I've gotten into the habit of repeating my calculations and writing it thus instead:

select [x]+[y] as A, [z]*([x]+[y]) as B from MyTable.

However, I now have some query fields that have so many calculations in them that I exceed the string length that Access allows for a query field. So is there a way to make the shorter SQL work consistently?

Any ideas appreciated.

Thanks!

PS: Here's the field I need to shorten:
AdjFcstDay: IIf(((Sum([AvgDaily])*First([forecastweeks])*5+nz(First([backlog]),0))/(First([forecastweeks])*5))+IIf([wiptotal]<(IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([lowwipflag]))*First([dailystddev]))),((IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([lowwipflag]))*First([dailystddev])))-[wiptotal])/5,IIf([wiptotal]>(IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([highwipflag]))*First([dailystddev]))),((IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([highwipflag]))*First([dailystddev])))-[wiptotal])/5,0))<0,0,(Sum([AvgDaily])*First([forecastweeks])*5+nz(First([backlog]),0))+IIf([wiptotal]<(IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([lowwipflag]))*First([dailystddev]))),((IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([lowwipflag]))*First([dailystddev])))-[wiptotal])/5,IIf([wiptotal]>(IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([highwipflag]))*First([dailystddev]))),((IIf(First(CDbl(nz([dailystddev],0)))<=0,0,xlnormsinv(First([highwipflag]))*First([dailystddev])))-[wiptotal])/5,0)))

 

[FoFa]

I would break the query into two, and do the basic calculations in the first query, then base the second query on the first (and any other tables) and do the more complicated calculations in that.