May I suggest that If the relationship of this type is based on the verse 1 below, we should be mentioned Cost Sheet material in INET as picture below . please consider this way.
1. Item A in INET is always equal to item A in INET.
2. Item A in INET can be equal to A or B or C in Cost sheet.
If the relationship is based on the verse 1, we should be mentioned Cost Sheet material in INET as picture below . please consider this way.