use exec, for example
use pubs
godeclare @lastnames varchar(100)
SET @lastnames = '''white'',''green'',''carson'''exec('select * from authors where au_lname in (' + @lastnames +')')
use pubs
godeclare @lastnames varchar(100)
SET @lastnames = '''white'',''green'',''carson'''exec('select * from authors where au_lname in (' + @lastnames +')')
set @po = '''aa'',''aa'',''bb'''
exec('select * from table where field1 in (' +@po + ')')