Hello Emily
The following formula may be all that you need:-
=IF(B2="","",IF(D2="Tuesday",C2+30,IF(D2="Friday",C2+34,"")))
You can drag it down as far as you need. It relates to Columns A:E with the formula in Column E.
I don't know what your spread sheet looks like so I've attached a mock-up spread sheet for you to play with. Click on a cell in Column E to see the formula displayed in the function bar. I've introduced a "helper" column(D) to extract the week day name from the dates in Column C. If "Attended" is not entered in the Status Column(B) then nothing happens in Column E. Have a play with Columns B & C to see how it works.
The helper column uses this formula:-
dragged down.
I hope that this helps.
Cheerio,
vcoolio.