Update Product master in CRM

We have replicated materials from R/3 to CRM 4.0. We have created a new category id and Hierarchy id and need to link it to the material. The category id will have the settype and the necessary attributes tied to the settype need to be populated.

WE have about 6000 materials and looking to automate this updation using a flat file. We have not been able to find a BAPI that we could use to update the material . Do you know what we could use to update the material master record in CRM with the above???

Thanks in advance

Umesh