I have a large spreadsheet where some data are similar. for Example

Robert $1000
Louis $600
Glen $350
Doreen $2300
Robert $500
Louis $600
Glen $750
Doreen $300
Robert $3000

I want to merge all Robert together, all Louis together and show as one Robert $4500. How can I do that ? Someone suggesed that I should use a Look up. Can someone give me the formula for this please ??