The code was developed for someone else many years ago and it appears that somewhere along the way, I modified it to do what someone else wanted.
The following should do a better job in your case:
Dim sourcea As Document, sourceb As Document, target As Document, Pages As Integer, Counter As Integer, targetrange As Range
Dim evenpage As Range
Set sourcea = Documents.Open(FileName:="...") 'Document containing the odd pages
Set sourceb = Documents.Open(FileName:="...") 'Document containing the even pages
sourceb.Repaginate
Pages = sourceb.BuiltInDocumentProperties(wdPropertyPages)
Set target = Documents.Add
target.PageSetup.LeftMargin = sourcea.PageSetup.LeftMargin
target.PageSetup.RightMargin = sourcea.PageSetup.RightMargin
target.PageSetup.TopMargin = sourcea.PageSetup.TopMargin
target.PageSetup.BottomMargin = sourcea.PageSetup.BottomMargin
target.AcceptAllRevisions
Counter = 0
While Counter < Pages
sourcea.Activate
Selection.HomeKey wdStory
ActiveDocument.Bookmarks("\page").Range.Copy
Set targetrange = target.Range
targetrange.Collapse wdCollapseEnd
targetrange.Paste
sourcea.Bookmarks("\page").Range.Cut
sourceb.Activate
Selection.HomeKey wdStory
ActiveDocument.Bookmarks("\page").Range.Copy
Set targetrange = target.Range
targetrange.Collapse wdCollapseEnd
targetrange.Paste
targetrange.Start = targetrange.End
targetrange.InsertBreak Type:=wdPageBreak
sourceb.Bookmarks("\page").Range.Cut
Counter = Counter + 1
Wend
sourcea.Range.Copy
Set targetrange = target.Range
targetrange.Collapse wdCollapseEnd
targetrange.Paste
sourcea.Close wdDoNotSaveChanges
sourceb.Close wdDoNotSaveChanges