Knowing what was modified? and/or setting a date field with a multiple selection field.

Knowing what was modified? and/or setting a date field with a multiple selection field.

In Opportunities, my company has created a multiple selection field called "Steps Taken." The user selects all of the options that apply and save.

I want to know the date each of these selections was added. Is that possible?

The API can tell me when something was modified, but I don't see where it tells me WHAT was modified. 

-M.Epler

PS - if it is not feasible to get the date or know what was modified, how might we design this field better in our CRM to capture that data?

Thanks!