error 017: undefined symbol "ReturnUser"

	para1 = ReturnUser(tmp);

ReturnUser(text[])
{
	new pos = 0;
	while (text[pos] < 0x21)
	{
		if (text[pos] == 0) return INVALID_PLAYER_ID;
		pos++;
	}
	new userid = INVALID_PLAYER_ID;
	if (IsNumeric(text[pos]))
	{
		userid = strval(text[pos]);
		if (userid >=0 && userid < MAX_PLAYERS)
		{
			if(!IsPlayerConnected(userid))
			{
				userid = INVALID_PLAYER_ID;
			}
			else
			{
				return userid;
			}
		}
	}
	new giveid;
	new GetPlayer[20];
	for (giveid=0; giveid<=MAX_PLAYERS; giveid++)
	{
	    if (IsPlayerConnected(giveid))
	    {
			GetPlayerName(giveid,GetPlayer,16);
			new space = (strfind(GetPlayer, text));
			if (space != -1)
			{
				return giveid;
			}
	    }
    }
    return userid;
}