insert space in front of any question, if a space is not present

The code below pads every cell in the range with a trailing space. As part of the same macro, I need to insert a space in front of any question mark (the character, not the wild card) where a space is not already present. How would I add this to the code?

Sub AddTrailingSpace()

Dim Sh1 As Worksheet
Dim Range As Range, cel As Range

Set Sh1 = ActiveWorkbook.Sheets(1)
With Sh1
    Set Range = Intersect(.UsedRange.Offset(1), .Range("k:k, m:m, o:o, q:q"))
        For Each cel In Range
            cel.Value = cel.Value & " "
        Next cel
End With
End Sub