VBA for validating data

[Godwin117]

I have this excel document that dates are entered in cells F12 and G12 to the last row, data validation works when someone enters the data, but the dates don't change. I would like to know if there is a vba I could use to validate those dates and have a message box that shows where the errors are located.

 

[Godwin117]

I'm allowed myself to make two buttons instead of one. It's more convenient, i think. Paste this to ThisWorkbook module.

Private Sub Workbook_Open()
Application.ScreenUpdating = False
On Error Resume Next

Dim iAF As Variant, iAG As Variant, iR&, lR&, d As Date: d = Date

lR = Cells(Rows.Count, 1).End(xlUp).Row
iAF = Range("F12:F" & lR).Value
    For iR = 1 To UBound(iAF)
            If iAF(iR, 1) > d Then
                Dim m As Integer, mp$, mt$
                mt = "Next?"
                mp = "Need to check Date in F" & iR& + 11
                    m = MsgBox(mp, 4 + 32, mt)
                        If m = 6 Then
                        Else
                            Exit Sub
                        End If
            End If
    Next
  
iAG = Range("G12:G" & lR).Value
    For iR = 1 To UBound(iAF)
            If iAG(iR, 1) < d Then
                mt = "Next?"
                mp = "Need to check Date in G" & iR& + 11
                    m = MsgBox(mp, 4 + 32, mt)
                        If m = 6 Then
                        Else
                            Exit Sub
                        End If
            End If
    Next

Application.ScreenUpdating = True
End Sub

This works great, Thank you, is there a way for it to skip if the cell is blank?

 

[LazyBug]

is there a way for it to skip if the cell is blank?

We need to replace the string

If iAF(iR, 1)>d Then

with

If iAF(iR, 1)>d and not IsEmpty(iAF(iR, 1)) Then

and

If iAG(iR, 1)>d Then

with

If iAG(iR, 1)>d and not IsEmpty(iAG(iR, 1)) Then

Try it (I typing from my phone, so could be wrong).

 

[Peter_SSs]

@LazyBug
You reported some errors in the above post. To correct them, please just make another reply here, pointing out the corrections.

 

[LazyBug]

Thanks for the answer, Peter_SSs.
I made a mistake in the second case.
The correct option will be

If iAG(iR, 1) < d and not IsEmpty(iAG(iR, 1)) Then

instead of

If iAG(iR, 1) < d Then