How To update the month number with conditions

[thanhvanchi]

Hello everyone!
Not sure if this is possible. I have sales figures for the year and I want to show the current month sales figures by Rep.
I have a column with the month in numerical value e.g. 9 = September, a column with the sales handler name, and a column with the sales figure.

So I want to be able to update the month number manually each month so from 9 to 10 when October starts, and for the cell to return the sales figure for that month, for the handler the cell relates to.
Thank's a lot.
QC: công ty chúng tôi chuyên dịch vụ internet fpt hưng yên và internet fpt hoà bình và internet fpt hải phòng cho quý khách.

[avk]

upload your sample file to get clear idea.