Trouble with Null value in query

[Middlemarch]

SELECT  Nz([Mode]) AS Expr1
FROM qryBB
WHERE  ((Nz([Mode]))<>4;

This works in Access but I need it to work without Nz()
Have spent hours trying IsNull Is Not Null etc but getting nowhere.
Can anyone help? Thanks.

[CJ_London]

Why do you need it to work without the nz function? If in a different environment, there are usually alternates

[ArviLaanemets]

Why Nz([Mode])?
As you compare [Mode] not equaling with 4 or contrary, we can assume that in source table Mode has some numeric value or is Null. Nz() without optional ValueIfNull argument determined returns an empty string, i.e. "", when Mode is Null. So you'll check is "" <> 4 then!!! And you want for some records Mode to be returned as a string, and for other records as a number!