Formula for bill of materials (BOM)

[izuanovic]

Hello everyone,

Let's say out of 10 components in BOM, component A appears 4 times in recipe/BOM. 

Out of those 4 -> 3 times the quantity should be fixed (which I know how to do) irrevelant to the batch size.

Now what I dont know how to do is to adjust the last, 4th time component A appears depending on the batch size. 

Formula for the 4th could be: '=total share of component A in the recipe * (batch/100) - all fixed amounts

Please, any help is much appreciated.