Selecting multiple cells - vba

Question

I have this code that check if the attachment size of the attachment is greater than 10MB. Now, if the attachment is greater than 10MB, it displays the file names on a msgbox then I want to select or highlight the cells that has this attachment greater than 10 MB but dunno how to do it.
Here's what I've tried:
Function checkAttSize()
Application.ScreenUpdating = False
Dim attach As Object
Dim attSize() As String
Dim loc() As String
Dim num As Long
Dim rng As Range
Set objOutlook = CreateObject("Outlook.Application")
Set objMail = objOutlook.CreateItem(0)
Set main = ThisWorkbook.Sheets("Main")
lRow = Cells(Rows.count, 15).End(xlUp).Row
efCount = 0
num = 0
With objMail
If lRow > 22 Then
On Error GoTo errHandler
For i = 23 To lRow
'attach.Add main.Range("O" & i).value
'totalSize = totalSize +
If (FileLen(main.Cells(i, "O").value) / 1000000) > 10 Then
ReDim Preserve attSize(efCount)
ReDim Preserve loc(num)
'store file names
attSize(efCount) = Dir(main.Range("O" & i))
'store cell address
loc(num) = i
efCount = efCount + 1
num = num + 1
found = True
End If
Next i
End If
End With
If found = True Then
MsgBox "Following File(s) Exceeds 10MB Attachment Size Limit:" & vbCrLf & vbCrLf & Join(attSize, vbCrLf) _
& vbCrLf & vbCrLf & "Please try removing the file(s) and try again.", vbCritical, "File Size Exceed"
'trying to select the cell addresses
For i = 1 To num
rng = rng + main.Range("O" & loc(i)).Select ' Ive also tried &
Next i
checkAttSize = True
Exit Function
End If
Exit Function
errHandler:
MsgBox "Unexpected Error Occured.", vbCritical, "Error"
checkAttSize = True
End Function
Thanks for the help.

Answer 1

No need to select the range. A single miss click by the user take take the focus away from the range. Also using .Select recklessly may cause run time errors. Color them instead.
After this line
If (FileLen(main.Cells(i, "O").value) / 1000000) > 10 Then
Add this line
main.Cells(i, "O").Interior.ColorIndex = 3
The cells now will be colored in red.
And in the end, alert the user with the message
If found = True Then
MsgBox "File(s) Exceeding 10MB Attachment Size Limit has been colored in red:"
End If