I'm trying to do an inventory spreadsheet for my store. Here is the problem.

Example. Mon-x amount Tues-received xamount Wed. xamount Fri.-xamount
Total xamount for week.

basically, an inventory count is done on mondays, wednesdays, and fridays.
I receive a truck on tuesdays. The problem is that I need to show a total
amount of what is in the store on Friday nights. But, I can't figure out the
formula to use where it will subtract mondays, wednesdays, and fridays ending
inventory to show what i have in the store. Plus, along with having received
items. What formula would i use for the "total" column?