Calculate required filament per extruder

I use PVA as a support material. As PVA is hygroscopic and gets moist when stored in open air, I store the PVA in a drying chamber. For each print I estimate how much PVA is needed and then only transfer that length to another spool. However, instead of estimating how much I need, it would be great if Slic3r simply could tell me! It already calculates the total required filament (both in mm and in cm³), but not per extruder. Is it possible to get that information, or to add this feature?

gcode viewer (gcode.ws) will show how much filament is used and let you check your gcode before printing. Not sure how it handles multiple extruders, but worth a try.

I'm familiar with gcode.ws. First it did not handle multiple extruders at all, but I contacted the developer (Alex Ustyantsev) and he changed that. It now handles multiple extruders, but only if they are on different axis, it does not react on extruder change commands. Unfortunately, the latter is what I need...\