working with forecasts/dates
 

I would like to look at a date within a cell and if the date is within a
certain range post an amount from another cell into the appropriate column.
For example: my columns are as follows: Vendor name, due date, amount, week
ending 9/7, 9/14, 9/21 etc. I want the formula to look at the due date and
determine which week ending date the amount should be in for forecasting
purposes. Does this make sense? How do I do it?