parameter for database selection

Hi All Experts,

As We know All the tables in sap b1 are same for different database.

I want that when i run crystal report it should prompt for parameter to select database,

and when I select particular database, data from that database should be viewed.

In Short I want parameter for database selection.

Note:I can login to any company,but when I run it should prompt me for different database.

Please Help....

Best Regards,

Gayatri Shukla.