thanks, it is good way... is there any other way to do this? just for learning, otherwise this works well

i checked the task usage view and couldnt see how else it can be done.

the only way i could think of was - (and i thought of it because a cumulative cost field exist in tas view), i entered durations in terms of cost , such as, if it is 7 day duration i entered $7 - just for the sake of seeing it , and not assigning any cost ofg course, i was just doing it by means of cost fields. i had no costs assigned in my project yet anyway.

then i pasted the date range and cumulative cost (duration) to excel... and made a graph. the results were almost the same.