CE39 is what's needed. I have it installed, but I no longer have the install file. I dug around and found the following notes I've collected on field programming. Maybe it will let you do what's needed...use at your own risk!
_____________________________________________
VX-900 Field programming
Yes, there is a way to do field programming. You need to short pins 3 and 7 of the external mic connector, then hold down the lamp and PTT button while powering the radio on. You will see "FIELD" in the display. (The "lamp" button is the bottom button below PTT.) Pins 3 and 7 are the 2nd and 4th pin down on the left side as you are looking into the connector on the side of the radio.
Then using the channel knob, select the function you want to program, and using the top and side Set buttons change the entries. For frequency, use the toggle switch to select MHz, tenths, hundredths and the top/side set buttons to change the applicable item. (The side "set" button is the top button above the PTT, and the top "set" button is the orange button.) After changing an entry, turn the channel knob to another position to "enter" the change. Power the radio off and back on to go back to normal operating mode.
With 512 channels, I really didn't need the ability to change frequency all that much, but being able to change/set tones in the field is significant for me. I wish that Vertex had made that a "user" accessible function.
The Radio Information Board - Index page
Dealer mode
Anyhow, I was looking for a way to get into those greyed-out dropdown menus in the VX900 software, which would allow you to change squelch hysteresis, squelch attack time, squelch release time, etc. What I ended up doing was running CE39Win.exe with every single switch possible (-a,-b,-c,-d…
until the menu items became ungreyed. Well, they never came ungreyed, but with the switch “-m”, a password dialog popped up. I tried “password” and the program started up, but the boxes were still greyed out. So, it turns out, “password” was not the password. So, after a little bit of resourceful hacking, I was able to find the password, which is “ansho-bango” (no quotes).
______________________________________________