OK, It seems that I was not clear enough.
My problem is next.
I need to write PL/SQL scripts that will be called from .bat file and I need to pass name of user(schema) to script.
For example:
This will be in test.bat file:
sqlplus scott/tiger @test.sql username_1
and now in test.sql I need to create variable that will take value username_1,
I tought I need to write somethink like this in test.sql:

CCLINT CONSTANT and here type of variable :='&1';
I have tried with VARCHAR2 but it didn't work,
Any idea how to solve this problem?

Thanks