Removing the mandatory field from a custom object

Hi guys

I am wondering if it is possible to remove the mandatory field that is created when you create a custom object or if you can change the mandatory field to something else, as I have a look up field to the company screen which could come off if I could get the company name to populate the Mandatory field somehow automatically, I tried creating a  work flow with a field update but failed an am not sure if this is even possible   L , any help or suggestions would be greatly appreciated

Thanks

James