Hi,
From my manual (mind you I am not Dash pilot
)
"
When the system is in TERMINAL MODE a green "TRM" will be displayed on the upper left corner of the EHSI next to "CRS". When an FMS Approach is activated, a green "APP" will be displayed on the upper left corner of the EHSI next to "CRS". In the EN ROUTE MODE there is no specific indication."
"The use of vertical navigation (VNAV) is prohibited when either "TRM" is not displayed on EHSI while the system is in the Terminal Mode, or "APP" is not displayed on the EHSI while the system is in the Approach Mode of operation."
Hope it helped.