Swap head pointer in circular linked list

[nyxxie]

struct looks like this:

struct ListNode;
typedef ListNode* ListType;
struct details
{
  char first_name[20];
  char last_name[20];
  int  start_number;
  int  end_number;
};

struct ListNode
{
  details data;
  ListType next;
};
ListType list = NULL;
ListType head = NULL;
ListType * PointerToHead = &head;

I have a circular linked list that i bubblesort, and the swap function for it now looks like this:

void Swap(ListType& a, ListType& b)//when called b is always a->next
{
  ListType prevNodeA;
  ListType tempPtr = a;
  ListType AfterNodeB = b->next;

  while(tempPtr->next!=a)//find the node before a
    {
    	tempPtr = tempPtr->next;
    }
  if(tempPtr->next==a)
    {
    	prevNodeA = tempPtr;
    }
  if(prevNodeA->next==head)//if it is head, assign b as head ?
    {
      b->next = prevNodeA->next;
      prevNodeA->next = a->next;
      a->next = AfterNodeB;
      b = head;
      PointerToHead = &b;
    }
  else
    {
      b->next = prevNodeA->next;
      prevNodeA->next = a->next;
      a->next = AfterNodeB;
    }
};

I am fairly certain that im swapping the pointers right, the problem lies in assigning the head, because it never reads the else part. The first time im calling the fuction, a is the head of the list and it is stuck in that loop.
Sort function:

void Sort(ListType* PointerToHead)
{
	ListNode *temp1;
	ListNode *temp2;

    for(temp1 = *PointerToHead ; temp1->next!=head ; temp1 = temp1->next)
    {
	for(temp2 = temp1->next ; temp2->next!=head; temp2 = temp2->next)
	{
	  if (Smallest(temp2->data, temp1->data))
	    {
	      Swap(temp1, temp2);
	    }
	}
    }
};

so my question is, how do i reassign the head while in a circular linked list?
(i only have a head node in the linked list, no tail). the pointer of the last node points to the head.