Code not running to last row

[gheyman]

I have code that is supposed to perform all the way to the last row that has data in column H

But it seems to stops right before the last two rows. So if I have all the way to row 739, its not putting data in 738 or 739 column 13

If I add data to H740 and H741 I get data in column M (13) for 738 and 739.

Help Please. I need it to go to the last row of data

ActiveSheet.AutoFilterMode = False
Application.Calculation = xlManual

Sheet11.Activate

Dim ws As Worksheet
Dim st1 As String, st2 As String
Dim a As Long
Dim cont As Long

  Set ws = ActiveSheet

  cont = Application.WorksheetFunction.CountA(ws.Range("h:h"))

  For a = 4 To cont
  
    If ws.Cells(a, 5) = 0 And ws.Cells(a, 7) = 0 Then
      ws.Cells(a, 12).Value = 1
      ws.Cells(a, 13).Value = 1
      
    End If
        
    If ws.Cells(a, 6) <> "" Then
      st1 = ws.Cells(a, 6)
      For B = a - 1 To 1 Step -1
        st2 = ws.Cells(B, 8)
        If st1 = st2 Then
          ws.Cells(a, 13) = ws.Cells(a, 12) * ws.Cells(B, 12)
         
          Exit For

        End If
      Next B
    End If
  Next a

 

[welshgasman]

CountA only counts cells that are not blank?

I generally use the code below on a column that has the data in the furthest row

lngLastRow = Range("A" & Rows.Count).End(xlUp).Row

 

[Fluff]

Change this

cont = Application.WorksheetFunction.CountA(ws.Range("h:h"))

to

Cont = Ws.Range("H" & Rows.Count).End(xlUp).Row