Which LOOKUP function to use and Keeping Formula Column Constant when Inserting Columns

Have a spreadsheet that another user helped me with a great function. I am wanting to tweak the function, but have not been able to quickly figure it out on my own.

Attached s'sheet shows 5 columns. The 5th Column (Check) locates a value from Column A from an array Columns D and E and then returns the difference in prices (sums) between Columns B and E. If there is no difference, it returns "Identical". If the string of text in Column A is not found, formula returns NA.

****I am wanting to do two things****
1. Move column F - the "Check" column over to column A.
2. I want to keep column A constant and have it work when, weekly, I insert two columns directly after column A with new weekly data. I looked in to using the "My Forumla" feature (Forumlas>Define Name), but could not seem to get it to work consistently.

Thank you so much!