Message doesn't show once - vba

Question

I don't understand why I get the error message repeated many times when data is inserted wrong more then 2 times i.e. column A. So if 3 mistakes are in column A, then the message pops up 3 times. I set Mwarning as boolean but I guess it is not set properly.
Can anyone guide me in solving this issue?
Dim aRec As Worksheet, bRec As Worksheet, wb As Workbook
Dim match
Dim Mwarning As Boolean
Dim c as long
Set wb = Excel.ActiveWorkbook
Set aRec = wb.Worksheets(1)
Set bRec = wb.Worksheets(2)
Application.ScreenUpdating = False
For c = 2 To aRec.Cells(Rows.Count, "A").End(xlUp).Row
match = Application.match(aRec.Cells(c, 1).Value, bRec.Columns(2), 0)
If IsError(match) And Not IsEmpty(aRec.Cells(c, 1)) Then
aRec.Cells(c, 1).Interior.Color = RGB(255, 0, 0)
MsgBox "Mistakes are in column A", vbInformation, "IMPORTANT:"
Mwarning = True
Else
aRec.Cells(c, 1).Interior.Color = RGB(255, 255, 255)
End If
Next c
If Mwarning = True Then MsgBox "No errors found!", vbInformation, "IMPORTANT:" ' if an error is set in column A, then do nothing, otherwise get the next message
Application.ScreenUpdating = True

Answer 1

EDIT :
Replace you msgbox in the loop by a log like this and add only one msgbox at the end of the sub :
Sub testMsg()
Dim aRec As Worksheet, bRec As Worksheet, wb As Workbook
Dim match
Dim c As Long
Set wb = Excel.ActiveWorkbook
Set aRec = wb.Worksheets(1)
Set bRec = wb.Worksheets(2)
Application.ScreenUpdating = False
Dim log As String
log = ""
For c = 2 To aRec.Cells(Rows.Count, "A").End(xlUp).Row
match = Application.match(aRec.Cells(c, 1).Value, bRec.Columns(2), 0)
If IsError(match) And Not IsEmpty(aRec.Cells(c, 1)) Then
aRec.Cells(c, 1).Interior.Color = RGB(255, 0, 0)
log = "Mistakes are in column A"
Else
aRec.Cells(c, 1).Interior.Color = RGB(255, 255, 255)
End If
Next c
If log = "" Then
MsgBox "No errors found!", vbInformation, "IMPORTANT:" '
Else
MsgBox log, vbInformation, "IMPORTANT:"
Application.ScreenUpdating = True
End Sub
You add a msgbox function in a loop MsgBox "Mistakes are in column A", vbInformation, "IMPORTANT:"
So I think that msgbox will be repeated every time if the IF condition is encountered.

Answer 2

You add a msgbox function in a loop MsgBox "Mistakes are in column A", vbInformation, "IMPORTANT:"
So I think that msgbox will be repeated every time if the IF condition is encountered.
Delete this.

Answer 3

EDIT: improved answer that leaves the cell coloring alone without adding another IF. Msg will only fire once, the Row locations will be reported in a single msgbox as the error string is built inside of your loop, be careful if there are many errors.
Dim aRec As Worksheet, bRec As Worksheet, wb As Workbook
Dim match
Dim Mwarning As Boolean
Dim c As Long
Dim rpt As String
Set wb = Excel.ActiveWorkbook
Set aRec = wb.Worksheets(1)
Set bRec = wb.Worksheets(2)
Application.ScreenUpdating = False
Mwarning = False 'Always, Always, Always set an intitial condition
rpt = "WARINING: Column A Errors are Found" & vbNewLine & vbNewLine
For c = 2 To aRec.Cells(Rows.Count, "A").End(xlUp).Row
match = Application.match(aRec.Cells(c, 1).Value, bRec.Columns(2), 0)
'Added the piece that if there is an error, check if the box has already fired = true,
'if it has NOT fired, then fire it once and not again
If IsError(match) And Not IsEmpty(aRec.Cells(c, 1)) Then
aRec.Cells(c, 1).Interior.Color = RGB(255, 0, 0)
Mwarning = True
rpt = rpt & "Error Found at Row: " & c & vbNewLine
Else
aRec.Cells(c, 1).Interior.Color = RGB(255, 255, 255)
End If
Next c
'You only want this to pop if no errors are found in the FOR LOOP
If Mwarning = False Then
'if no error was found report this message
MsgBox "No errors found!", vbInformation, "IMPORTANT:"
Else 'error was found in column A so Mwarning is true
MsgBox rpt, vbInformation, "IMPORTANT:"
End If
Application.ScreenUpdating = True

Answer 4

You have set Mwarning as Booleanand you set it to True when a mistake is found, but you do not check for its value in the loop. So, the if in the loop should also check for Mwarning value.