Expression on the bases of filters

[capriconuser]

i have this formula 

net_pre - tax_prem

and these filters

code in ('12','13,'16','90') and type in ('abc','def','xyz') and type2 in ('general)

now i want to create expression using formula and filters.. how i do that .. 

[Claudiu_Anghelescu]

sum( {<code={'12','13,'16','90'}, type={'abc','def','xyz'}, type2={'general'}>} net_pre)
-
sum( {<code={'12','13,'16','90'}, type={'abc','def','xyz'}, type2={'general'}>} tax_prem)

[capriconuser]

one more thing please i have this condition also 

(A.Code Is Null Or (A.Code Is Not Null And A.MClass Is Null))

how to modify in the answer you provided .. 

sum( {<code={'12','13,'16','90'}, type={'abc','def','xyz'}, type2={'general'}>} net_pre)
-
sum( {<code={'12','13,'16','90'}, type={'abc','def','xyz'}, type2={'general'}>} tax_prem)

[capriconuser]

any help please

[Claudiu_Anghelescu]

This condition should be added to the expression above?
(A.Code Is Null Or (A.Code Is Not Null And A.MClass Is Null))

Or you need a new expression but using this condition?

[Claudiu_Anghelescu]

If you need a new expression try this:

sum({<A.Code={''} + (A.Code={''}, A.MClass={''})>} net_pre)
-
sum({<A.Code={''} + (A.Code={''}, A.MClass={''})>} tax_prem)

[capriconuser]

why + sign here ? because in this expression
A.Code Is Null Or (A.Code Is Not Null And A.MClass Is Null)

there is OR

[Claudiu_Anghelescu]

In Set Expression in QlikView, the sign + is equal ti OR