Drop Down (Select Multiple) + Filtering

Hi All,

I have a quick problem that I am looking for some help on. I would like to create a dropdown list that allows me to select multiple and then filter for any individual value.

Consider:

Row 1 - A
Row 2 - A,B
Row 3 - A,B,C

I would want to filter for all values which contain B. I know that I can do this by simply filtering by -> Contains -> B, but I would rather have a filter in which I can select either A,B,C, and all of the rows which contain the selected value or values remain. I already have the dropdown w/ select multiple figure out, it is just the filtering issue.