Change custom field to multi-select picklist?

Change custom field to multi-select picklist?

I would like to change a custom field from its current state of only selecting one option and edit this field so that multiple choices can be selected.  (Change to a multi-select picklist rather than single select).
Is this possible?
I already have hundreds of records with information in the current field so I do not want to delete it complete and create a new field.

Nandri/Thanks