I need help, desperately. What the hell is the BACKCOURSE HOLD switch for?

apr mode for ILS/BC. no glideslope

Ther is a difference between ILS/BC and the two-localizer setup.
The last one isnt implemented in FS... together with the infamous side switching NDB's the russians are fond of. simply switching the whole navaid set from one side of the runway to the other side while keeping the frequencies the same

Yeah! Thanx a lot, guys (espeically Nexus)!!!!!!!

Since I am new to the board it is taking me a little time to read through all the posts, many offer
very good information.  I have noticed the very good post by Nexus re LOC (BACK CRS) approaches.  Airports with runways which support such operations have published procedure (approach plates) the same as any ILS or VOR , etc, approach.  Many of the back course
approaches are disappearing and being replaced with normal LOC, VOR, or GPS procedure.  I do not know if FS2002Pro supports any actual back course procedure, but for any of you wishing to use the LOC for a back course approach, I might recommend something to you which may help with the "backward instrument presentation."

As an example, if you plan on making a back course approach to runway 27, and will be using the
LOC for rwy 09, tune NAV1 to the localizer, THEN set you HSI to the recopical of the rwy 27 heading.  In other words, if your approach is to rwy 27, then set you HSI to 090 (which would be the course you would fly if making the ILS to rwy 09).  Once the LOC has been captured for your approach to rwy 27,  this will cause your course deviation indicators to read like a normal ILS approach, and not the opposite from what you are used to. (If the deviation is to the left, then a left correction is needed.)  But remember, your HSI is set up to flying a reciprocal heading and if a missed approach is necessary, then your heading information will be 180 degrees off until you change the HSI.  By the way, this only works on equipment with HSIs.