Yes, you're right.

One gets blind after a fair amount of time staring at all those lines.

Of cause that with the A restrictions there is the only possible B exception.

The user can start from tab A, or from tab B.

So the requirements run from A to B or from B to A.

My possible calculation approach comes from my data model where I write the "business rules".
There I have the allow/not allow/need.

Now that I'm at the database model, I was just wondering if going further with calcs was the best/good way.
Although I prefer by far scripting.

On top of that, I have the feeling that there is somewhere a conflicting situation/moment in the requirements.
It is just a feeling, can't really put a finger on it (now).
Because the requirements are coming "from above" (common temp problem, linked to constant changes), there is not much I can do, unless coming up with the physical proof that it doesn't work.

I will start with the zillions and painfully crawl through each possibility, until it comes to a screechy halt (or not).

Thanks for answering John, appreciate.

JM