I've done exactly this. But you have to parse out each part of the combined text list. This works for up to 20 names and of course you can add on.
var text value = ToText([Combined Text of Emails Field]);
ToUserList(
ToUser(Trim(Part($value,1,";"))),
ToUser(Trim(Part($value,2,";"))),
ToUser(Trim(Part($value,3,";"))),
ToUser(Trim(Part($value,4,";"))),
ToUser(Trim(Part($value,5,";"))),
ToUser(Trim(Part($value,6,";"))),
ToUser(Trim(Part($value,7,";"))),
ToUser(Trim(Part($value,8,";"))),
ToUser(Trim(Part($value,9,";"))),
ToUser(Trim(Part($value,10,";"))),
ToUser(Trim(Part($value,11,";"))),
ToUser(Trim(Part($value,12,";"))),
ToUser(Trim(Part($value,13,";"))),
ToUser(Trim(Part($value,14,";"))),
ToUser(Trim(Part($value,15,";"))),
ToUser(Trim(Part($value,16,";"))),
ToUser(Trim(Part($value,17,";"))),
ToUser(Trim(Part($value,18,";"))),
ToUser(Trim(Part($value,19,";"))),
ToUser(Trim(Part($value,20,";"))))
------------------------------
Mike Tamoush
------------------------------
