I hope that someone can help with this data collection

A1 B1
a 4 digit no a 1 digit no
A2 B2
a 4 digit no a 1 digit no

In another cell for data collection I need to have the data form cell A1 and
at the side a total of B1 or B2 etc etc if a1,A2 etc are the same number
I hope that I have explained this properly, what it is for is a time sheet
where the same job ( a 4 digit no) across a number of days has had various
hours spent at this task. I need to have a collection athe base of the report
totalling all the hours spent on a particular job