Find & Replace On Protected Sheets Fails

I am attempting to run a macro that will do a find and replace on a protected sheet but this is not working. I am using the following code to Protect all Sheets, which I found on this site when workbook opens using the Workbook Open Event and uses UserInterFaceOnly :

Private Sub Workbook_Open()
Dim wSheet As Worksheet

For Each wSheet In Worksheets
wSheet.Protect Password:="111", _
UserInterFaceOnly:=True
Next wSheet
End Sub

And then a find and replace similar to this:

Sub FindAndReplace()
Selection.Replace What:="w", Replacement:="a", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
ReplaceFormat:=False
End Sub