Autopopulate??? I Think... (See attached).

[jedDallas]

For the life of me I can't figure this out.

I have a spreadsheet with June 1, through June 30, in Colum A It is a tracking spreadheet.
If i place a # representing qty shipped in cell B3 I need a formula that will auto-populate this amount 7 days from the shipped date ( A3) and place it in the delivery colum. In this case it would be placed in C11 representing 7 days from the original ship date of June 1. Does this make sense?
Please see attached