Decision between Multiple Alternatives formula

Hi Experts,

I got situation where we want to Decision between Multiple Alternatives

Scenario:

We have a Process Chain P1 which will run on every month 5th working day and this chain contain 2 local chains C1 and C2.

Now we want to run local chain C1 (without running Main Chain)  on every weekend. But this local chain should not trigger independently on 5th working day, It should trigger based on main chain.

What my question is what should be the functions used in formula of Decision between Multiple Alternatives as per the above scenario.

Please provide suggestions.