Built a little spreadsheet at work. The main function looks something like this:
=IF($D6>V$5,0,IF((DATEDIF($D6,V$5,"m")+1)>$G6,0,((IF(V$5<$D6,0,IF($B6="DB",VLOOKUP($G6,DB!$B$3:$BD$9,IF($D6>V$5,0,DATEDIF($D6,V$5,"m"))+2),VLOOKUP($G6,DBB!$B$2:$BD$9,IF($D6>V$5,0,DATEDIF($D6,V$5,"m"))+2))))*$C6)-$U6))
I need a drink.