Need a formula for "Days Open" with a Turn In Date and Date Closed

I have a spreadsheet in which I track delinquent reports. In the first column is the date that the asset was turned in. I'd like to throw in a "days open" column because at certain intervals, we need to send follow up emails. When the entry is closed, I'd like for the column to stop counting. It can either return a 0 in the days open column, or it can return the number of days the asset was open. Either way would work as I already have it set up to automatically turn green once the entry is closed.

I'm working on Excel 2013.

Columns are set up like

TIN DATE, STATUS, TIN BY, NSN, TIN DOC, SN, RC, UNSERV, LOC, DAYS OPEN, CC, SHIP TO, SHP DOC, CLOSED DATE

Any help would be greatly appreciated.

Update:
I added two columns. One column was closed date-TIN Date, second column was TODAY()-TIN Date. Then I put =IF(B4="Closed", K4,L4)

B column= Status
K column= closed-tin
L column= today-tin

Then I hid the K and L columns

If anyone has a cleaner way, I'd love to know.

Hi, welcome to the forum

What you need to understand about dates and times in excel is…

a date is just a number representing the number of days passed since 1/1/900...and then formatted in a way that we recognize as a date. So, for instance, today (Sun 08 Jul 2018) is actually 43289

Time is actually a decimal part of 1 (day), so 06:00 AM is 0.25, 12 noon is 0.5 and 18:00 (or 6 PM) is 0.75

With that said, if your dates are REAL dates, and not text looking like dates, you could just add something like...
=if(cell-with-closed="closed,"Closed", today()-"date-started")
You can replace the "closed" with whatever you want - "" will give you a cell that appears empty

If you still have a problem, upload a small (clean) sample workbook (not a pic) of what you are working with, and what your expected outcome would look like.

To attach a file to your post,
click advanced (next to quick post),
scroll down until you see "manage file",
click that and select "add files" (top right corner).
click "select files" find your file, click "open" click "upload" click 'done" bottom right. click "submit reply"

Once the upload is completed the file name will appear below the input boxes in this window.
You can then close the window to return to the new post screen.