Loop thru a datalist within a datalist

Trying to loop thru a nested datalist. I am able to get the parent datalist but not the nested datalist. Any help is appreciated.

Dim slist As DataList = TryCast(dlSupplyCategory, DataList)
For Each row As DataListItem In TryCast(slist.FindControl("dlSupplies"), DataList).Items   <----- comes back null reference
    msg = msg + "<td>" & CType(row.FindControl("ItemNoLabel"), Label).Text & "</td>"
Next