New Post: Add Column in a list programmatically?

How about adding a Site Column to a list using SPServices? I am trying to add a Lookup Column, which I made as a Site Column referencing a list in the root site, to a lists in subsites. I have tried using:

<Field Name="New List Column" DisplayName="New List columns" Type="Lookup" List="{lookup-list-guid}" />

This worked perfectly for lookup lists in the subsites, but not for a lookup list located in the root list.

Any help/insite is appreciated.