How to assign classifcation to a product

Hello Experts,

I hope you are doing good.

I an facing an issue in SAP GTS System that there is a requirement as below,

Through a program or function module i have to assign classification(grouping and export numbering i.e data will be stored in /sapsll/ctsnum table) to a product(Ex:product number is 00000102121).

Please suggest me if you know any standard function modules to do this requirement. Its urgent.

Thank you on advance.

Regards,

KBS