Rand(columname) in SQL Server : overflow due to varchar conversion to int

I am stuck with a problem regarding SQL Server and RAND and varchar to int conversion overflow.

I am trying to assign a random value to CONTRACT_id.

For instance:

SELECT CONTRACT_ID, RAND(CONTRACT_id) 
FROM EUROPE

CONTRACT_ID has values such as FA15630 and 013789 and is of type VARCHAR(50). It seems that RAND() function is not capable of converting varchar values to int. I've tried bigint, NEWID doesn't suit my requirements as well because i have duplicated contracts that should have the same RAND set up number.

Hi SMor, thank you for your clarification. What I am trying to accomplish is having the following

Contract_id                     Assigned Value
--------------------------------------------------
FA1630                          1
0136589                         2
FA63987                         3                    
FA1630                          1

Thanks!

I appreciate your help. Thanks!