Tracking expenditures by budget lines

Thanks for this great forum.

I am trying to track expenditures by budget lines. What I have is (i) totals for various budget line expenditures, (ii) a drop down menu to choose which budget line is being charged and (iii) a place to input the value of each expenditure.

How do I enable my spreadsheet to do the following:
once a budget line is chosen from the dropdown menu, add the expenditure value input to the total amount of the particular budget line.

I have attached a sample worksheet setup. I appreciate any help you can provide.

I am not sure what you want, so here are two alternatives (see encl.)
//Ola

The formula =SUMIF($A$6:$A$51,H20,$B$6:$B$51) is exactly what I was looking for!

Many, many thanks.

Thanks for the feedback
Ola