Help? ...thanks..

you could use the "int mod" that you have in G_Damage to identify the weapon that do damage to the player IE

if(mod == MOD_FREEZEGUN) {
//freeze the player
}

try this example code to prevent people from walking:
(I don't have the code to look at, I've done this in my mod Elite Squad Arena)
but here's an example:

code:

---

if (mod == MOD_FREEZEGUN) {
     client->ps.powerups[PW_FREEZE] = level.time + 10000; // 10 seconds in milliseconds
}

---

and then in g_active.c where the player speeds are handled:

code:

---

if (client->ps.powerups[PW_FREEZE])
    client->ps.speed = 0;
else
    client->ps.speed = g_speed;

---

I don't know if all the code is correct, but it should give you a clue about how to do.