You need another table for the formula's ingredients, where each ingredient will have its own record.
Thanks for your response. Could you elaborate a bit more? I've made the new table but I can't see a way forward.
Not sure where you're stuck with this. The Ingredients table needs (at least) the following fields:
• FormulaID (foreign key to the Formulas table)
• BatchID (foreign key to the Batches table)
• API_ID (for narrowing down the selection of BatchID)
In addition to the basic structure of:
Formulas -< Ingredients >- Batches
you need a helper relationship (using another occurrence of the Batches table):
Ingredients::API_ID = Batches 2::API_ID
Define your value list to use values from Batches 2::BatchID, show related only starting from Ingredients.