How To Use Varchar With Int Column

Hi,
I am writing a SP in MSSQL. One of the parameted is VARCHAR type
which have comma seperated INT vlaues. I want to use this varible in
WHERE clause against INT type coloum. how do I achive this.

eg. DECLARE @CompanyTypeIDs VARCHAR(200)
SET @CompanyTypeIDs = '1,3,2'

Currently I am using it as
SELECT CompanyTypeID FROM Company WHERE CompanyTypeID IN (1,2,3)

CompanyTypeID is of INT type.
But I want to replace the consts with the Parameter passed as below

SELECT CompanyTypeID FROM Company WHERE CompanyTypeID IN
(@CompanyTypeIDs) - but this is not giving any result.

Please let me know the solution.

Many Thanks,
Mahesh