how do i log my workout while wearing a 30 lb iotv

so long story short i made a deal with my husbands (in the army) that i would get up at 430am this morning with him (when he goes to pt) and wear his IOTV (30 lb bullet proof vest with all the fixins) while i do my morning walk......problem is theres no option for that on MFP i walked 1.5 miles at a 3.5 mph pace, wearing about 30lbs in gear and i weigh 145....how do i calculate how many calories i burned AND log it!!!