Hi Peter,
I've just test it in my machine. And it can update the field "Name" on UDT.
Dim oDT As SAPbobsCOM.UserTable = oCompany.UserTables.Item("TRANSIT_LOCATION")
oDT.GetByKey("0312")
oDT.Name = "TEST"
oDT.Update()
If Not oDT.Update() = 0 Then
SAP_APP.SetMessage(oCompany.GetLastErrorDescription)
End If