Merging Empty Cells when Last Cell in Column&Row is Empty

[helpexcel]

This code works great until the last column is blank. So the last column in row 22 is blank and should be merged with column 21. Colum 22 has data, but row 22 doesn't. It's reading the last column as the end of the spreadsheet. I've tried to play around with the changing the last column calculation to a different row, but no luck. Thanks for the help!

Dim c3 As Long, c4 As Long
    c3 = 3
    Do
        If .Cells(22, c3 + 1) = "" Then
            c4 = .Cells(22, c3).End(xlToRight).Column
            If c4 < Columns.Count Then
                .Range(.Cells(22, c3), .Cells(31, c4 - 1)).HorizontalAlignment = xlCenterAcrossSelection
                c3 = c4
            Else
                Exit Do
            End If
        Else
            c3 = c3 + 1
        End If
    Loop
End With

 

[helpexcel]

got rid of the Do/Loop and used For/Next with range defined by lc2 and it works.

Dim c3 As Long, c4 As Long, lc2 As Long, lc3 As Long
lc2 = .Cells(12, Columns.Count).End(xlToLeft).Column
lc3 = Columns.Count
 
 c3 = 3
For M = 3 To lc2
        If .Cells(22, c3 + 1) = "" Then
            c4 = .Cells(22, c3).End(xlToRight).Column
            If c4 < Columns.Count Then
                .Range(.Cells(22, c3), .Cells(31, c4 - 1)).HorizontalAlignment = xlCenterAcrossSelection
                c3 = c4
            ElseIf c4 = lc3 Then
                .Range(.Cells(22, c3), .Cells(31, (lc3 - (lc3 - lc2)))).HorizontalAlignment = xlCenterAcrossSelection
                c3 = c4
            End If
        Else
            c3 = c3 + 1
        End If
    M = M + 1
Next