Check a file called "logiccommandset" (its in \MOD SDK\CnC3Xml\GlobalData). This file, i think, is what controls the build menu's and the extra commands (like deploy for the mcv). U probably need to add an entry to this in the command set for the construction yard (id="GDIConstructionYardCommandSet"),
for example
CODE
<LogicCommandSet
id="GDIConstructionYardCommandSet">
<Cmd>Command_ConstructGDIPowerPlant</Cmd>
<Cmd>Command_ConstructGDIRefinery</Cmd>
<Cmd>Command_ConstructGDIBarracks</Cmd>
<Cmd>Command_ConstructGDIWarfactory</Cmd>
<Cmd>Command_ConstructGDICommandPost</Cmd>
<Cmd>Command_ConstructGDIAirTower</Cmd>
<Cmd>Command_ConstructGDIMedicalCenter</Cmd>
<Cmd>Command_ConstructGDIArmory</Cmd>
<Cmd>Command_ConstructGDISpaceCommandUplink</Cmd>
<Cmd>Command_ConstructGDIWatchTower</Cmd>
<Cmd>Command_ConstructGDIGolumCannon</Cmd>
<Cmd>Command_ConstructGDIAABattery</Cmd>
<Cmd>Command_ConstructGDITiberiumSilo</Cmd>
<Cmd>Command_ConstructGDITerraformingStation</Cmd>
<Cmd>Command_ConstructGDIIonCannonControl</Cmd>
<Cmd>Command_ConstructGDICrane</Cmd>
<Cmd>Command_ConstructGDISurveyor</Cmd>
-- Try enter something like the following --
<Cmd>Command_ConstructGDIWall</Cmd>
-- End of possible entry --
<Cmd>Command_PackGDIMCV</Cmd>
<Cmd>Command_SelfRepair</Cmd>
<Cmd>Command_Sell</Cmd>
</LogicCommandSet>
or replace gdi with nod or alien, for nod and scrin respectively. oh, and for the files - you have to make a mod directory in MOD SDK\Mods with the correct file\folder structure that the game uses. Have a look in the
README, i think it may have examples. Failing that, have a look at the sample mods structure and always fiddle with things. If it dont work, then change something until it does. Hope this helps