Thanks Godfrey and Kevin for the replies. At first I thought I should flatten things out, but then went with (what I hope) is more of a MM way. I have controls bound to different sources, and after reading "Synchronizing Controls with Different Data Sources" in the help, am using this code, which seems to work fine.

protected override void HookPostNavigate()
{
	CadCall boCadCall = (CadCall)this.GetBizObj(typeof(CadCall));
	CadCallDataSet.CadCallRow currentRow = boCadCall.CurrentCadCallRow;
	CmnAgency boCmnAgency = (CmnAgency)this.GetBizObj(typeof(CmnAgency));
	CmnAgencyDataSet dsAgency = (CmnAgencyDataSet)boCmnAgency.GetCurrentDataSet();
	DataView dv = dsAgency.GetDataView("dvAgencyByPK");
	int position = dv.Find(currentRow.CmnAgencyFK);
	this.txtIncidentNumber.DataBindings[0].BindingManagerBase.Position = position;
}

My first attempt at using relationships didn't seem to work, but if that's a better way, I'll look into it some more.

Thanks,
Mike