Alert for Percentages in Column

I have a sheet with people and each row lists their name and the project name and the percentage of their time they spend on that project each month. If they work on more than one project they will show up in multiple rows. A separate row for each project they work on. I am trying to find a way where I can get an alert or conditional formatting when that person's total percentage in the column exceeds 100%. Since all staff are on this sheet it can't just SUM the column in whole. Seems like a formula would be able to do this but I cannot figure it out. Any ideas? Thanks.