INDEX, MATCH multiple values in single row, return header value(s)

[grrliz]

I have a RACI chart outlining responsibilities, accountabilities, etc. for various team members on multiple projects. (See attached doc.) Using this data, I would like to be able to look up a given project and return, for example, the names of the team members who have been assigned the letter C for that project.

I've found other examples of how to do this when the value being looked up is arranged in a column rather than a row, and I've found examples that return a single header rather than multiple headers if there are multiple values, but nothing that will look up multiple instances of a value in a row and then return (potentially) multiple header values.

Helper columns are fine, VBA is not due to how this workbook will be used by others. There may be cells that contain two different letters, in which case the formula will need to be able to return headers for both "C" and "R C" columns, for instance.

Thanks!

RACI_chart_test.xls.xlsx