treeview (repeating nodes??)

I use the following code to generate nodes in a treeview.
The problem I have is that the underlying table only contains 2 records but the treeview displays 4 nodes.
It in fact repeats the first 2 records.

For Each rowAuthor In ds.Tables("Calls").Rows
nodeAuthor = New TreeNode()
nodeAuthor.Text = rowAuthor("CALLDATE")
TreeView1.Nodes.Add(nodeAuthor)
next rowAuthor

Can anyone tell me what I am doing wrong and how I can solve this wee
quandry.

Thanks in Advance