[AccessD] sorting query on 'named' collumn and use 'named' collumn in where criteria of a query

Dear list,

in qeuries i use a lot of functions to format a value, or to get
'calculated' values, these functions get 'named' collumns (like .... AS
clientnumber). This works fine.
However when i want to use this named collumn in the WHERE - statement or in
the ORDER BY statement and i use the collumn name this doesn't work. Ik i
use the same function again in the WHERE and ORDER BY statement this works
fine, but it slows down the qeury, because the function has to be executed
more times.
Can i use the named collums in the WHERE and ORDER BY statement and if so
how do i do that?

I am working with A2k on WINXP and WIN2kProffesional

Thanks.

Bert-Jan