Interest with random payments spreadsheet

Hey Im trying to work on a spreadsheet and I have little experience...This is as far as my brain and little knowledge will take me. I will attach a sample of my spreadsheet...Anyway, to the point, I am trying to add interest to multiple accounts; all having different deposit dates/beginning dates....and from years going as far back as 2004.

So as you can see from the attachment - in "Account #4" - P19 should have the interest in that cell but it ended up in P21.. also on same "account" interest is in O21, when it should be in O20...

Any suggestions on improving this spreadsheet is welcome! (Keep in mind I am a novice)

Thanks!Interest-Security Deposits-Test.xlsx

Hints at least? A Link to a site that will help?.....Anything?

Pfft...Nm Noone here is able to help I guess. You can delete this post. I'll just do it manually.