[regalis]

I never used it too

But maybe something like this:

new Weapons[32]
new numWeapons, i, weapon
get_user_weapons(id, Weapons, numWeapons)
for (i=0; i<numWeapns; i++)
{
   weapon = Weapons[i]
   if ( weapon == CSW_HEGRENADE )
    {
        client_print ( id , print_chat , "[AmxX] You already own one," )
    }
    else if ( money < ( multi * g_he_nade ) )
    {
        new bool:noMoney = true
    }
    else
    {
        new bool:giveGrenade = true
    }
}
if(noMoney)    client_print(id , print_chat, "[AmxX] You do not have enough money." )

if(giveGrenade)
{
    give_item (id , "weapon_hegrenade" )
  cs_set_user_money ( id , money - ( multi * g_he_nade ) )
  client_print ( id , print_chat ,  "[AmxX] Thank you for using Emergency Ammo!" )
}
return PLUGIN_HANDLED

greetz regalis

PS: thx 4 karma