IS it possible to have multiple culture codes in a cms repeater?

For example, a site with 4 cultures:
en-us (default)
en-ca
fr-ca
en-gb.

In my cmsrepeater i would like to display only: en-us, en-ca, en-gb.

I've tried this and it works to display both en-us and en-ca:
<cms:CMSRepeater ID="repeaterContentList" runat="server"
SelectOnlyPublished="true"
ClassNames="custom.Asset"
CombineWithDefaultCulture="true"
CultureCode="en-ca"
OrderBy="PublicationDate DESC" />

However when I add en-gb, it falls over and only displays en-us:
<cms:CMSRepeater ID="repeaterContentList" runat="server"
SelectOnlyPublished="true"
ClassNames="custom.Asset"
CombineWithDefaultCulture="true"
CultureCode="en-ca; en-gb"
OrderBy="PublicationDate DESC" />

What am I doing wrong?