Newbie help

Okay, Im making a projector with a simple texture change on touch script, i was wondering if it is possible to add in a next/previous buttons from a freebie vendor? Or is there anything I have to add or change?

 default
{
  
     touch_start(integer total_number)
    {
        integer number = llGetInventoryNumber(INVENTORY_TEXTURE);
        float rand = llFrand(number);
        integer choice = (integer)rand;
        string name = llGetInventoryName(INVENTORY_TEXTURE, choice);
        if (name != "")
            llSetTexture(name, ALL_SIDES);
    }
}