Would an array formula be useful to find the total?

Hello there,

I hope you can understand from this explanation.

Imagine B2 to M2 to contain monthly figures in terms of hours to be spent on a section of a project, N2 to include the total money coming in for that project.

I'd like to find the incidence of the hours over the total, obtaining how much is worth a given month.
This was solved by doing N2*Given Month/(SUM(B2:M2)).

Prospects Jan-16 Feb-16 Mar-16 Apr-16 May-16 Jun-16 Jul-16 Aug-16 Sep-16 Oct-16 Nov-16 Dec-16 Money coming in
Test 0.00 0.00 0.00 0.00 228.75 228.75 228.75 228.75 0.00 0.00 0.00 0.00 £27,280.00

Total FTE time £- £- £- £- £6,820.00 £6,820.00 £6,820.00 £6,820.00 £- £- £- £- £27,280.00


The challenge is that I have X many rows, and I don't know in advance how many these could be.
I'd like to have a formula that could surface a range of cells, being able to add new rows if required without changing the formula.

I thought the array formula could have been useful, but I can't figure out how I can get them working giving this particular scenario.

Any helps?
Andrea