Sum of columns to right - update when new column inserted

Hi
I'm trying to create a spreadsheet tracking time total time spent on a list of projects.

Please see below and attached sample.

Each day I want to insert a new column to the right of the Total column (please note that I don't want to add the column after the last column) and enter the time spent in minutes.

P.No. Total 18Oct 17Oct 16Oct
001 30 10 10 10
002 25 15 10 0

..So I'm trying to work out formula to insert in the total column that will add all columns to the right (even when the number of columns increases)

..Ideally the formula would also convert the number of minutes into hours and minutes eg 05:20 for '5 hours 20 minutes' ie. 320minutes

Thanks for any assistance