Is it possible to have a piece of equipment impart a new mode to another?

[Dammann]

I am still writing a gdf to cover the Demolisher template. I'm trying to write up an ammunition type that automatically adds a new mode to a ranged weapon. Is this an impossible thing to do? I notice that High-Tech and Ultra-Tech do not have this sort of operation (unless I failed to find it).

I am writing it in these terms (and not getting it to work):

Spoiler:  

Encoding=UTF-8
Version=3
* The version information above MUST be the first line of the data file, 
* or the first line AFTER the 'Encoding=UTF-8' line, when that is included.

Description=User created data file containing custom traits saved from within GCA.
Program=4.0.423

[AUTHOR]
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*
* GURPS(R) Character Assistant Data File
* Created: Sunday, May 27, 2012
* Requires GCA v4 or later!
*
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[EQUIPMENT]
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<_Demolisher Weapons>
"Firebolt",baseweight(0.125),basecost(28),page(p3/36:7),mods(Equipment, Crushing/Imp Class Quality, Arrow, Demolisher Gear),
	 uses(count*1),precountcost(28),acc(-1),damage(1d-1),dmg(1),damtype(cr ex),cat(Basic Set, Basic Set - Muscle-Powered,
	 Ranged Weapons, _Muscle-Powered Ranged Weapons, _Muscle-Powered Ranged Weapons - Basic Set, Basic Set, 
	 Basic Set - Muscle-Powered Ranged Weapons, _Muscle-Powered Ranged Weapons, _Muscle-Powered Ranged Weapons - Basic Set, 
	 Demolisher Gear), gives(to EQ:Crossbow[::Dungeon Fantasy: Demolisher Firebolt])

Crossbow (ST%choiceList%), weaponst(%choice%), basecost(150), baseweight(6), mode(Barbed-head), damage(@thr(me::weaponst)+4), damtype(imp), lc(4), techlvl(2), acc(4), calcrange(yes), rangehalfdam(me::weaponst*20), rangemax(me::weaponst*25), rof(1), shots(1(4)), minst(7†), bulk(-6), skillused(SK:Crossbow, ST:DX-4), page(B276), notes([3]), cat(Basic Set, Basic Set - Muscle-Powered Ranged Weapons, _Muscle-Powered Ranged Weapons, _Muscle-Powered Ranged Weapons - Basic Set),
	itemnotes({An arrow or bolt for a bow or crossbow is $2. A dart for a blowpipe, or a lead pellet for a prodd or sling, is $0.1. Sling stones are free.}),
	description(TL:2 LC:4, Dam:thr+4 imp Acc:4 Range:ST*20/ST*25 RoF:1 Shots:1(4) ST:7† Bulk:-6 Skill:Crossbow Notes: [3]), mods(Equipment, Bow Quality),
	x(#ChoiceList(name(choice), title(Bow ST), text(A Bow/Crossbow must be assigned a ST score. This is the ST of the bow itself; a character normally uses a bow with ST equal to his own ST.), picksallowed(1), method(bynumber), list("  1","  2","  3","  4","  5","  6","  7","  8","  9"," 10"," 11"," 12"," 13"," 14"," 15"," 16"," 17"," 18"," 19"," 20"," 21"," 22"," 23"," 24"," 25"," 26"," 27"," 28"," 29"," 30"," 31"," 32"," 33"," 34"," 35"," 36"," 37"," 38"," 39"," 40"," 41"," 42"," 43"," 44"," 45"," 46"," 47"," 48"," 49"," 50"," 51"," 52"," 53"," 54"," 55"," 56"," 57"," 58"," 59"," 60"," 61"," 62"," 63"," 64"," 65"," 66"," 67"," 68"," 69"," 70"," 71"," 72"," 73"," 74"," 75"," 76"," 77"," 78"," 79"," 80"," 81"," 82"," 83"," 84"," 85"," 86"," 87"," 88"," 89"," 90"," 91"," 92"," 93"," 94"," 95"," 96"," 97"," 98"," 99","100")))


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*Equipment Modifiers
[Modifiers]
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<Bow Quality>
Dungeon Fantasy: Demolisher Firebolt, +0, page(P3/36:7), group(Bow Quality, _Demolisher Gear), shortname(Firebolt),
	addmode(Firebolt,
			damage(1d-1),
			damtype(cr ex),
			lc(%copyfirst),
			acc(3),
			calcrange(%copyfirst),
			rangehalfdam($eval(%copyfirst-5)),
			rangemax($eval(%copyfirst-5)),
			rof(%copyfirst),
			shots(%copyfirst),
			minst(%copyfirst),
			bulk(%copyfirst),
			skillused(%copyfirst),
			rcl(%copyfirst),
			notes(%copyfirst)_
			)

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[Groups]
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<Bow Quality>
Dungeon Fantasy: Demolisher Firebolt

The really salient part is the bit at the end of [Equipment] "Firebolt." I included Crossbow simply to bring all the pieces to one place.