I need to add data if sites match in one column (C). If they match, then
corresponding cell data from Column (B) are added together and as a sum in
Column D. If there is not a duplicate match it would be great if the cell
just carried over to Column D. The duplicates are not consistent and single
sites are intermixed. Column B is numeric, Column C is text

Example

B C D
1 s234 1

2 s235
5 s235 7
4 s236 4
5 s237
1 s237 6


Thank you for your input.