Trailing Stop Loss Tracking

Hi everyone this is my first post. So I apologize in advance if it isn't written properly or in the right place. But here is my question.
I am trying to keep a trailing stop loss for an investment portfolio in excel. So far I got the stock quotes to feed. I have columns for stop%, Purchase price, previous close (this feeds from msn stock quotes), % Gain-Loss, High Price, Stop Price, % From stop. The formula I entered for the high Price is =IF(C5>D5,C5,D5) which is =IF(Purchase Price> Previous close, Previous close, Purchase price). The problem is that I want the high price to remain the same value if it is higher then the Purchase price. How can I do that?

Also This is a separate question but the way I have it set up I have to refresh my spreadsheet every day the market is open otherwise I will miss a closing price. Is there any way I could avoid having to open and refresh the sheet each day?

I have attached a copy of the spreadsheet if that helps.

Stop Loss Tracking 7.7.2015.xlsm