Forecast dates on the basis of partial confirmation

Hi,

I am having a tough time handling this requirement. Pls help.

I have a scenario, where i want system to propose a new finish date on every schedule update on the basis of current actual data.

For example,

An activity has a duration of 10 days and work of 100 m3. start date: 1st Apr & finish date is 10th Apr.

And activity is linearly distributed.On 5th Apr, if confirmation is 40 m3 of work completion instead of a planned completion of 50 m3,

then on re-scheduling, system should propose a new finish date for the activity. ie. for remaining 60 m3,

it shud automatically add another 8 days (60/8 = 8 approx.because the current rate of work is 40hrs/5 days= 8 hrs per day) to the current actual finsih date ( 5th Apr) and hence on next schedule update, the current finish date shud be 5 + 8=13th April instead of 10th april.

Regards,