Hi Sridhar,
Updating directly in SAP tables is not recommended.Yes as mentioned it may create some inconsistencies.
Use the help of where used list by clicking on the field of the table /SAPAPO/MATLWH and see any Bapis/Function modules are available for doing this.Worst case you can go for a BDC upload.
Also you can request SAP via OSS to help providing an appropriate code.
Regards,
Kannan