Finding first empty cell under a given cell range

[OfficeUser]

I am currently using this code to plot out cell locations based on where I enter info into a cell. So for example if I put a letter into cell G25, then the corresponding grid coordinates would be D-3 and then that would be placed into the next empty cell under A33.

When I started using this code I never had info upto A57. After that all rows were hidden. I have since added more rows and now when I plot, my coordinates fall into the first empty cell of column A, cell A68. How do I get it go back to looking at the first empty cell under A33? Thanks.

Sub Plots(Target)
  Dim Grid As Range
  Dim Locus As String
  Dim NextCell As Range
  Dim R As Long, C As Long
    Set Target = Target.Cells(1, 1)
    Set Grid = Range("C20:AA28")
      If Not Intersect(Target, Grid) Is Nothing And Not IsError(Target.Value) Then
        If Target.Value <> "" Then
         Set NextCell = Cells(Rows.Count, "A").End(xlUp)
           If NextCell.Row < 33 Then Set NextCell = Range("A33")
         R = Target.Row
         C = Target.Column
        NextCell.Offset(1, 0) = Cells(R, "B") & "-" & Cells(29, C)
      End If
      End If
    Set Target = Target.Cells(1, 1)
    Set Grid = Range("AC20:BC28")
      If Not Intersect(Target, Grid) Is Nothing And Not IsError(Target.Value) Then
         If Target.Value <> "" Then
           Set NextCell = Cells(Rows.Count, "AD").End(xlUp)
           If NextCell.Row < 33 Then Set NextCell = Range("AD33")
         R = Target.Row
         C = Target.Column
         NextCell.Offset(1, 0) = Cells(R, "B") & "-" & Cells(29, C)
       End If
      End If
End Sub