Provided the tables are in the body of the document and not in headers footers, text boxes etc, and are similar to that shown, then the following should work.
Code:
Sub NumberTables()
Dim oTable As Table
Dim i As Long, j As Long
Dim oCell As Range
i = 1
For Each oTable In ActiveDocument.Tables
For j = 2 To oTable.Rows.Count
Set oCell = oTable.Cell(j, 1).Range
oCell.End = oCell.End - 1
oCell.Text = i & Chr(46) 'This is what goes in the cells!
i = i + 1
Next j
Next oTable
lbl_Exit:
Set oTable = Nothing
Exit Sub
End Sub