Forecast Schedule

Dear All, 

I am currently monitoring a schedule which is having budgeted expense cost assigned to engineering, procurement and construction phases. The performance percent is achieved by Activity % complete x weight (budgeted expense cost). The accural type for engineering and procurement activities is 'end of activity' while that for construction activities is "uniform over activity duration" so that start variance for constrction activites can be noticed easily. The %complete type is physical % complete. Now the problem...

The schedule is updated and when i make current schedule baseline of itself and assign it then current performance % complete and schedule % complete for engineering and procurement are equal. This makes sense since the accural type is end of activity. But for construction the performance % is not equal to schedule %. The schedule % is greater than performance % as it is being calculated on the basis of actual duration / BL duration * 100. For eg. if phyical % of an activity is 2% the schedule % is showing 66%, since activity started long back. Now to have forecast progress figures, the construction does not show correct figures as it starts calculating from 66% to the future data date.

Is there any way to do this in a better way to have correct forecast values for construction?

Please help..