get variable values from table!!

Hi all,

how can i do this. I don't want to hard code the package variable values when i want to deploy package from dev to test or prod.

Is there a way i can store in table and have it passed in when package execute. I know you can set the configuration file with xml or sql but need steps what to store in table or file.

also how to execute config file before ssis package execution takes place!!

Thanks