Create an excel formula to concatenate multiple cells into one cell with an if condition

I think this should be an easy request for a Excel guru, but I am not that. I need a formula that I can apply to every cell in a column that will concatenate values from multiple columns with an if condition. If the values are the same in another column then concatenate the value. I will upload a sample file of what I am looking for. I will try to describe the logic base on the file. The spreadsheet has a list of tests with Test IDs and Test Names. There is a column for the Location ID that the available test id/test name need to concatenate with ";" as a separator and fill the cell. This way all available tests for that location will be in one cell with a ";" separated between them. I need to be able to apply the formula to a file with 20,000 tests so the formula needs to work if pasted in every cell for a column.