If then else logic in expression builder for calculated column

[Techno]

I need to add a calculated column at the end of a select query that runs on table1(which is linked table) by expression builder, the logic is-
Calculated Column Value = If (table1.columnname(x) = "abc") then 1 else (table1.columnname(y).value)
How to do it? Any help greatly appreciated.

As a workaround to the above I tried to run an update query on linked table and it rightly failed.

[xps35]

You need to use the IIF function.

IIF(X = "abc", 1, Y)

[Techno]

Thank you...