Best price in combination with secondary price list

Good Morning!

Can you give me an advise for the following issue:

At the moment every customer has one price list and some (default) modifiers.

For every special offers we configure every 4 weeks an extensive modifier with about 4000 "new price" positions.

This procedure is very time-consuming, but we don't know another way, because some customers have better standard prices than the special offers.

If we use a primary and a secondry price list for the special offers the clients always get the price from the fist price list and sometimes that's the more expensive one.

I think we need something like a best price option for the choice between the primary and the secondry price list.