AutoFilter to find blank cells - excel

Question

I am trying to apply an autofilter in VBA for three different criterias in the same field. Once I have applied the filter I would like to find all those cells that are blank, can anyone advise?
Sub ApplyAutoFiler()
Dim ws As Worksheet
Dim I, j, NumberOfErrors As Long
IsErrors = False
Set ws = Sheets("Assessments")
NumberOfErrors = 0
Dim Z As Range
Set Z = Cells(4, 3).EntireColumn.Find("*", SearchDirection:=xlPrevious)
If Not Z Is Nothing Then
NumberOfRows = Z.Row
End If
For I = 4 To NumberOfRows
With ws
.AutoFilterMode = False
.Range("W4:AA4").AutoFilter Field:=1, Criteria1:=Array("A", "B", "C"), Operator:=xlFilterValues
.Cells.SpecialCells(xlCellTypeBlanks).Interior.Color = 65535
.AutoFilterMode = False
End With
Next I
End Sub
I ended up doing this as a nested if statement
If Range("W" & i).Value = "A" Or Range("W" & i).Value = "B" Or Range("W" & i).Value = "C" Then
If Range("AD" & i).Value = "" Then
Range("AD" & CStr(i)).Interior.ColorIndex = 3
NumberOfErrors = NumberOfErrors + 1
End If
End If

Answer 1

This seemed to get me close (it also assumes you have a worksheet called "Assessments"):
Sub ApplyAutoFiler()
Dim ws As Worksheet
Set ws = Sheets("Assessments")
With ws
.AutoFilterMode = False
.Range("A:AZ").AutoFilter Field:=23, Criteria1:=Array("a", "b", "c"), Operator:=xlFilterValues
.Cells.SpecialCells(xlCellTypeBlanks).Interior.Color = 65535
.AutoFilterMode = False
End With
End Sub

Answer 2

I know this treads had been quite long. But just want to share. To filter out blank cells, you could use autofilter using the following criteria:
Worksheets("sheet name").Range("A1").autoFilter Field:=18, Criteria1:=(Blanks)
"Field" refers to the column numbers. As for "Criteria1", it can be either
Criteria1:=(Blanks)
or
Criteria1:="="
or
Criteria1:=""

Answer 3

Something I just discovered today about filtering for blanks using VBA code. Be sure to include this in ALL code where you need to have blank cells:
' Get Rows with blanks
WorkRange.AutoFilter Field:=1, Criteria1:="=", Operator:=xlOr, Criteria2:="=" & ""
' Hides Rows with blanks ... same idea with the "<>" for operator
WorkRange.AutoFilter Field:=1, Criteria1:="<>", Operator:=xlOr, Criteria2:="<>" & ""
The first criteria gets true blank cells and those cells with hidden/non-printable characters, the 2nd criteria gets those cells containing an empty string. Excel user-interface handles this nicely, but VBA code requires both criteria.
This undocumented caveat just cost me several hours of debugging, not to mention a few choice words from my manager about "I thought we were removing the blanks from these columns..."
Just thought I would share, in the hopes of saving you all some headaches.

Answer 4

You don't need VBA for this. You can use Conditional Formatting for this. See this example
In the CF rule, set this formula
=AND($AA5="",OR($W5="a",$W5="b",$W5="c"))
ScreenShot
If you still want VBA then see this
Sub Sample()
Dim blnkRange As Range, rng As Range, aCell As Range
Dim ws As Worksheet
Set ws = ThisWorkbook.Sheets("Assessments")
With ws
'~~> Sample range for testing purpose
Set rng = .Range("W4:AA11")
.AutoFilterMode = False
With rng
'~~> Filter on "a","b","c"
.AutoFilter Field:=1, Criteria1:=Array("a", "b", "c"), Operator:=xlFilterValues
'~~> Then filter on blanks on Col AA
.AutoFilter Field:=5, Criteria1:="="
'~~> Using offset. Assuming that Row 4 has headers
Set blnkRange = .Offset(1, 0).SpecialCells(xlCellTypeVisible).Cells
End With
.AutoFilterMode = False
End With
'~~> This will give you the blank cells in Col AA
If Not blnkRange Is Nothing Then
For Each aCell In blnkRange
'~~> Color the blank cells red in Col AA
If aCell.Column = 27 Then aCell.Interior.ColorIndex = 3
Next
End If
End Sub