I have created a customized field similir to Resource Names called " Owners"

I have entered multiple values in the list.

When i try  to assign multiple Owners to a Task it doesn allow me to do it. Im only allowed to select one at a time.

Does anyone know how to do this??

I thought by selecting first value followed by comma and selecting second value would work but it only shows the second one as being selected.

Please help !!!