how to lock weeks in the config

Good day

I am creating a measure that needs to be locked for actual weeks, no problem.

In future weeks it needs to be locked for a specified number of weeks and then plannable thereafter.

So for Sales :

If ACWeek then ACSales else planned

But in planned : If lead time= 5 weeks then lock 5 weeks from elapsed +1 else plan

Can you please let me know if this is possible and what calcs i would need to create to achieve this

Many thanks