@Rosemary_Black Okay, so it sounds like your relationships are:
Logs ==ref==> Components SubParts ==ref==> Components
The first relationship is saying that each Log has a Component. This means that each Component has many Logs.
The second relationship is the same: each SubPart has a Component, and each Component has many SubParts.
If I understand correctly, you’re saying that you want each SubPart’s quantity to be updated based on some input in the Logs table.
This can’t work, though. To see why, imagine that you have log1 and log2. Both of those logs reference component15, which has subpart8 and subpart3.
What should the quantity of subpart8 and subpart3 be? They are related to multiple logs (log1 and log2), so they have no notion of a single quantity.
So, with your data, there’s not really a good way to do this.