Answer
Use the full window-control path syntax instead: :i_hWndFrame.frmWindowName.controlName — for example, :i_hWndFrame.frmEmployeeObjective.cmbPerformancePeriod to retrieve a combo box named cmbPerformancePeriod on the frmEmployeeObjective window. This direct reference works even for fields that don't show up as an available shortcut under the System Info tab.