我怎样才能推迟活动

我想延迟一条指令的执行，同时不执行任何其他指令
这是程序

public async void parcours_anim(Queue<int> f, noeud[] Arb_b, LabelExpression[] Lbls_A)
{
    int val = 0;
    while (f.ToArray().Length != 0)
    {
        val = f.Dequeue();
        index = Recherche_index(val, Lbls_A);
        //Stop here before executing this instruction for like 2seconds
        Arbre[index].Fill = Brushes.Blue;
        // and then continue
    }
}