Initial upload. Not currently functional as a mod. Includes some slightly refactored source code as well as the original mission this was debuted in zipped up as reference + example of usage.

functions/fn_vehicleUnload.sqf

@@ -0,0 +1,93 @@
+/*
+	Author: Clarky
+	Usage: 	
+		[
+			"CLF_fnc_VehicleUnloaded",
+			[_target, _caller, _depot]
+		] call CBA_fnc_serverEvent;
+
+	Intended to be run by an event handler call from a vehicle unload action from a player on a valid supply vehicle
+	
+*/
+
+params ["_vehicle", "_player", "_depot"];
+
+if (!isServer) exitWith {};
+
+if (isNull _vehicle) exitWith {hint "Vehicle ain't exist";};
+if (isNull _player) exitWith {hint "Player ain't exist";};
+if (isNull _depot) exitWith {hint "Depot ain't exist";};
+
+if !(_vehicle getVariable ["isSupplyVehicle", false]) exitWith {hint "Vehicle ain't supply vehicle";};
+
+private _vehicleCurrent =
+    _vehicle getVariable ["currentMateriel", 0];
+
+private _transferRate =
+    _vehicle getVariable ["transferRate", 50];
+
+private _depotCurrent =
+    _depot getVariable ["currentMateriel", 0];
+	
+private _depotMax =
+    _depot getVariable ["maxMateriel", 300];
+
+private _freeSpace =
+    _depotMax - _depotCurrent;
+
+if (_freeSpace <= 0) exitWith {
+
+    [
+        "CLF_ShowMessage",
+        [
+			1,
+			0,
+			"Depot is already full."
+		],
+        _player
+    ] call CBA_fnc_targetEvent;
+};
+
+if (_vehicleCurrent <= 0) exitWith {
+
+    [
+        "CLF_ShowMessage",
+        [
+			2,
+			0,
+			"Vehicle has no materiel available."
+		],
+        _player
+    ] call CBA_fnc_targetEvent;
+};
+
+private _amount =
+    (_transferRate min _freeSpace)
+    min _vehicleCurrent;
+
+_vehicle setVariable [
+    "currentMateriel",
+    _vehicleCurrent - _amount,
+    true
+];
+
+_depot setVariable [
+    "currentMateriel",
+    _depotCurrent + _amount,
+    true
+];
+
+[
+    "CLF_ShowMessage",
+    [
+		0,
+		0,
+        format [
+            "Unloaded %1 materiel. Depot now contains %2/%3.",
+            _amount,
+            _depot getVariable ["currentMateriel",0],
+            _depotMax
+        ]
+    ],
+    _player
+] call CBA_fnc_targetEvent;