This example uses the AnnotationGroupCount property to determine the number of groups on an image. Then it uses the GetAnnotationGroup method to get the group names.
Private Sub cmdListGroups_Click()
Dim intNumGroups As Integer
Dim strGroupName As String
Dim intCount As Integer
'find out how many groups are on the page
intNumGroups = ImgEdit1.AnnotationGroupCount
Load frmGroupList
'Since index values of GetAnnotationGroup start with
'0 have to loop one less than the number of groups
For intCount = 0 To intNumGroups - 1
strGroupName = ImgEdit1.GetAnnotationGroup(intCount)
'write names of groups to a listbox
frmGroupList.AnnoGroups.AddItem (strGroupName)
Next intCount
frmGroupList.Show
End Sub