excel hide rows with error values based on dropdown change - vba

Question

I would like to hide rows in column B9-B40 when Index/Match formula returns "N/A" , now I managed to get it done in VBA when the table is static but I have a dynamic table based on drop-down selection which means the number of N/As returned can be different for each time drop-down selection changes.
Here is what I have right now which hides the rows with N/A based on current drop-down selection, my dropdowns are in C2,C3 and C4. But it doesn't takes any further change in the dropdown into consideration afterwards. I am not very competent with the VBA so any help would be great.
Thanks.
Option Explicit
Sub hide_if_error()
Dim MyCell As Range, Rng As Range
Set Rng = Range("B9:B40")
For Each MyCell In Rng
If IsError(MyCell) Then
MyCell.EntireRow.Hidden = True
End If
Next MyCell
End Sub

Answer 1

You can do
Range("B9:B40").SpecialCells(xlCellTypeFormulas, xlErrors).EntireRow.Hidden = True
You will need a test in advance that errors are present though.
That might look like:
Option Explicit
Public Sub hide_if_error()
With ThisWorkbook.Worksheets("Sheet4")
.Range("B9:B40").EntireRow.Hidden = False
If Evaluate("=SUM(IF(ISERROR(" & .Range("B9:B40").Address & "),1))") > 0 Then '<==check if any errors present
.Range("B9:B40").SpecialCells(xlCellTypeFormulas, xlErrors).EntireRow.Hidden = True
End If
End With
End Sub
If necessary, you could link the above to a worksheet change or dropdown change event so it is fired each time there is an update using the dropdown(s)
For example:
If you data validation was in C2:C4 you would put in the code pane for the sheet the following event code:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo ErrHand
If Not Intersect(Target, Range("C2:C4")) Is Nothing Then
Application.EnableEvents = False
hide_if_error
End If
ErrHand:
Application.EnableEvents = True
End Sub
Note:
The worksheet event code goes in the code pane associate with sheet 4:
The other code goes in a standard module (module 1 here):
Example run: