Budget reallocation - reallocate money from 1 budget to another???

Hello all!

We have a situation where we are having money spent from 1 original Budget to be used for work on another secondary Budget. and this other secondary budget has a separate and different revenue source. And this other budget needs to "pay back" the original budget for the money it "borrowed". Specifically Budget 1 is a "consultant" budget with money set aside for consultants, and Budget 2 is a "benefits" budget with money sourced from a benefits partner. But, the same consultant is doing the work and it was easier/quicker to use the same