Help with formula - v look up ????

[Fifi2506]

Hello lovely people
My first post - yay
Be gentle with me !!!!!
I have something that I could do with some help on
I have quite a large spreadsheet of data
I don't think what I'm trying to do is difficult but I haven't found the solution when I've tried
I have a column a with three or four different categories a,b,c,d - there are multiples of each in this column each row has a financial value
I need a formula in a separate cell which identifies that the row contains category a then finds the financial value and sums all these values
Then same for b etc
I would be very grateful for your help
Many thanks in advance
F