Programming help - Can apex alert at certain reservoir volume remaining?

[tech4x4]

This may have been answered already but I was unable to find it. My question is can an alert be set when a reservoir connected to a DOS reaches a certain volume remaining? I know this is tracked already on the Apex but i'm not sure if "volume left" of the reservoir is available for programming e.g. if dos_4_1 < 400 then on.

Thanks in advance!