Correctly Calculating Projected Available Hours between a start and end date

I am trying to figre out the correct measure to show "Projected Hours" for future possible assignments for resources.  The Gantt chart works easy enough.  It is pulling Start and End date from a spreadsheet, and it works perfect and will change depeding on which opportunity I select.  Where I need help is getting that to translate into projected hours in hte matrix.  The totals by person are correct, but the monthly splits are not accurate.  I would want someone with a Dec 1 - June 30 assignment to show 160 or 168 or whatever the correct monthly split for each month.  Alternatively, the Julius resource that has a few short term engagements shows the correct monthly split, but the incorrect total.  December actually works perfect, but it does not flow through to other months.  any help would be much appreciated.