how do I make this update lol

local t = Def.ActorFrame {

    -- noteskin part
    LoadActor( THEME:GetPathB("_noteskinstuff/bottom",ntype) ) .. {
        Name="Fill";
        InitCommand=cmd(y,SCREEN_CENTER_Y-100;x,SCREEN_CENTER_X+180;diffuse,1,0,0,1);
    };
    Def.Sprite {
        Texture=( THEME:GetPathB("_noteskinstuff/top",ntype) );
        InitCommand=cmd(y,SCREEN_CENTER_Y-100;x,SCREEN_CENTER_X+180);
    };
};


-- update function to change it actively
local function Update(self)
    local ntype;

    if GetUserPref("NoteskinType") == "5" then
        ntype = "part bar";
    elseif GetUserPref("NoteskinType") == "4" then
        ntype = "part circle";
    elseif GetUserPref("NoteskinType") == "3" then
        ntype = "part ITGC";
    elseif GetUserPref("NoteskinType") == "2" then
        ntype = "part ITGM";
    else
        ntype = "part DDR";
    end;
end;

t.InitCommand=cmd(SetUpdateFunction,Update);

return t;