Conditional Validation using IIF?

Hi Guys,

I need to write a validation script that has some common fields and some conditional. Can I use the IIF function to specify the validation formula?

e.g.

Common parts

Conditional

Field 1 IS NOT NULL AND Field 2 IS NOT NULL AND Field 3 IS NOT NULL AND ( IIF(COUNTRY='USA', (Field 4 IS NOT NULL AND Field 5 IS NOT NULL), (Field 6 IS NOT NULL AND Field 7 IS NOT NULL)))

I probably can do a separate script  like (USA AND 1 AND 2 AND 3 AND 4 AND 5) OR (<>USA AND 1 AND 2 AND 3 AND 6 AND 7)    but it may exceed 1024 characters also it would require duplication of all those common fields.