Thank you. I was looking to join two columns at a time, not every column into one cell, but added one line and it worked. Then repeated the set, just changing the cell numbers I wanted to merge. Thanks!

Sub CellMerge()
Application.ScreenUpdating = False
Dim Tbl As Table, Rng As Range
For Each Tbl In ActiveDocument.Tables
With Tbl.Rows(1)
If .Cells.Count > 2 Then
Set Rng = .Range
Rng.Start = .Cells(2).Range.Start
Rng.End = .Cells(3).Range.End
Rng.Cells.Merge
End If
End With
Next