Insert Node at specific Index

[002comp]

Hello Friends I am creating Insert function which is adding nodes to end of List but I want to Insert at specific Index. Any Ideas? Here is the Code :

void Insert(Node** apList, Node* apNode, int aIndex)
{
Node* tmp = NULL;
int len = 0;
while((*apList) != NULL)
{
tmp = (*apList);
apList = &((*apList)->next);
len++;

}
     (\*apList)= (struct Node\*)malloc(sizeof(struct Node));

(\*apList)->num = apNode->num;
(\*apList)->next = NULL;

if(tmp)
	tmp->next = (\*apList); 

}

How can I insert at aIndex ? regards Y