put this line between 331 to 340
PHP Code:
public fw_TakeDamage(victim, inflictor, attacker, Float:damage)
{
if( get_pcvar_num( knife_on ) == 0 )
return HAM_IGNORED;
if( is_valid_player( victim ) && get_user_weapon(attacker) == CSW_KNIFE )
{
SetHamParamFloat(4, damage + knife_model[attacker]);
return HAM_HANDLED;