Using Lookup to distribute amount over a given duration

Hello,
I'm trying to do what Primavera simply does but with Excel.
I have few activities with their durations start and finish times and their total amount and I want to determine the cost for every week.
Now I need a function to automatically place the Amount/Duration for each activity in its place.
For Example, Activity A with a 5 weeks duration starts at week 1 and finishes at week 5 with an amount of 50,000$
It means that week 1 will have 10,000$ and so on till week 5 and the same with all other activities.
I want the formula to re-distribute the amount over the duration if I changed the start or finish times.
Is that possible?
Thanks