Stored Proc Using Variable As Fieldname In Select Statment

Using SQL Server 7 I am trying to modify an existing stored proc and make it more flexible. The below example represents the first part of that proc. The temp table that it should return is then used by another part of the proc (this query represents the foundation of my procedure). I need to figure a way to change the SQL Select statement, choosing between C.CONTRACTCODE and CB.EMPLOYERCODE on the fly. The query below will run but no records are returned. I am starting to believe/understand that I may not be able to use the @option variable the way I am currently.

I've tried creating two SQL statements, assigning them as strings to the @option variable, and using EXEC(@option). The only problem with this is that my temp table (#savingsdata1) goes out of scope as soon as the EXEC command is complete (which means I can not utilize the results for the rest of the procedure). Does anyone know how I can modify my procedure and incorporate the flexibility I've described?

Thanks,

Oliver

CREATE PROCEDURE test
@ContractCode varchar(10),
@dtFrom datetime,
@dtTo datetime,
@Umbrella int

AS

declare @option varchar(900)


if @umbrella = 0
set @option = 'c.contractcode'
else
set @option = 'cb.employercode'

select
c.claimsno,
c.attenddoctor,
c.patientcode,
p.sex,
cb.employercode
into #SavingsData1
from claimsa c inner join Patient p
on c.patientcode = p.patientcode
inner join claimsb cb on c.claimsno = cb.claimno
where
@option = @ContractCode and c.dateentered between @dtFrom and @dtTo
and c.claimsno like 'P%' and p.sex in('M','F') and c.attenddoctor <> 'ZZZZ'

select * from #SavingsData1