Here's a macro that will allow you to sort a datasource that is in the form
of a Word table so that the records (in their original order will print down
then across rather than across then down.  You should be able to just copy
and paste your Excel data into a Word document so that you have a table on
which you can run the macro.

' Macro to assign numbers to data source so that it can be sorted to cause
' labels to print down columns
Dim Message, Title, Default, labelrows, labelcolumns, i As Integer, j As
Integer, k As Integer
Message = "Enter the number of labels in a row"    ' Set prompt.
Title = "Labels per Row"    ' Set title.
Default = "3"    ' Set default.
' Display message, title, and default value.
labelcolumns = InputBox(Message, Title, Default)
Message = "Enter the number of labels in a column"    ' Set prompt.
Title = "Labels per column"    ' Set title.
Default = "5"    ' Set default.
labelrows = InputBox(Message, Title, Default)
ActiveDocument.Tables(1).Columns.Add
BeforeColumn:=ActiveDocument.Tables(1).Columns(1)
ActiveDocument.Tables(1).Rows(1).Range.Cut
k = 1
For i = 1 To ActiveDocument.Tables(1).Rows.Count - labelcolumns
   For j = 1 To labelrows
       ActiveDocument.Tables(1).Cell(i, 1).Range.InsertBefore k + (j - 1) *
labelcolumns
       i = i + 1
   Next j
   k = k + 1
   i = i - 1
   If k Mod labelcolumns = 1 Then k = k - labelcolumns + labelcolumns *
labelrows
Next i
ActiveDocument.Tables(1).Sort FieldNumber:="Column 1"
ActiveDocument.Tables(1).Rows(1).Select
Selection.Paste
ActiveDocument.Tables(1).Columns(1).Delete