float deltaz = 0.2;
vector sit_target;

UpdateSitTarget()
{
    key user = llAvatarOnSitTarget();
    if(user)
    {
        vector size = llGetAgentSize(user);
        vector pos = llGetPos();
        vector my_new_local_position = (sit_target + <0.0, 0.0, deltaz>);
         sit_target = my_new_local_position;
        llSetLinkPrimitiveParamsFast(llGetNumberOfPrims(),[PRIM_POS_LOCAL,my_new_local_position]);
       // return;
    }
    else
    {
        llUnSit(user);
    }
}

default
{
    state_entry()
    {
        llSitTarget(<0.0, 0.0, 1.0>, ZERO_ROTATION);
        sit_target = <0.0, 0.0, 1.0>;
    }

    touch_start(integer total_number)
    {
        UpdateSitTarget();
    }
}