Hi Uma Shankar,
The BOM Created for a Material will carry a BOM Group # and this can be used to alter the Specific BOM which has to be changed. Please check the Transaction CS05.
Please Go through the Below Link to get Further Clarification.
Changing one Alternative in a Multiple BOM - BOMs (PP-BD-BOM) - SAP Library
and also Try CEWB workbench.
Regards,
VVJ
