Data loaded at aggregate level in a custom measure is not diassgregating

We have a custom measure having hierarchy customer site + item + day.

We are trying to load the data at customer + item + month level. It is a challenge to load the data for every customer site + item combination.

Have already seen the Oracle note suggesting to load the data at the lowest level, but I am looking for any possible workaround wherein I can have the custom measure at a lower level and load the data at a higher level .