Need help speeding up Clear cells and merged cell

[SHELTONUNDERDOG]

Hello, I am two codes that I am calling when I click an icon in office 365's Excel. The two VBA's that I have, I found online looking for a code to do this process. I am not a VBA writer so that is why I am stuck in this spot right now. I ran the code and it took a little over two minutes to run. I know it could be faster if the two items did not look at every cell on the active sheet, but only the area that I allow people to input info. N3:AZ500 is my range that I need these two to look at instead of the whole sheet. Can anyone help out on changing the Range? I understand what the code is doing, it's just the Dim Rng As Range and such is where I get lost. Thanks again.

'THIS WILL CLEAR OUT ANY MERGED CELLS WHERE THE PROTECTION OPTION IN FORMAT CELL IS NOT SELECTED TO LOCKED
Sub ClearMergedCells()
    Dim Rng As Range, cel As Range, rClearA As Range
    Set Rng = ActiveSheet.UsedRange
    For Each cel In Rng
        If cel.MergeCells And cel.Locked = False Then
            If rClearA Is Nothing Then
                Set rClearA = cel
            Else
                Set rClearA = Union(rClearA, cel)
            End If
        End If
    Next cel
    rClearA.ClearContents
End Sub

'THIS WILL CLEAR OUT ANY UNMERGED CELLS WHERE THE PROTECTION OPTION IN FORMAT CELL IS NOT SELECTED TO LOCKED
Sub ClearUnlockedCells()

    Dim WorkRange As Range
    Dim Cell As Range
    Set WorkRange = ActiveSheet.UsedRange
    
    For Each Cell In WorkRange
        If Cell.Locked = False Then Cell.Value = ""
    Next Cell

End Sub

'THIS CALLS THE ABOVE TWO CODES AND RUNS THEM
Sub CLEAN_SHEET()
Call ClearMergedCells
Call ClearUnlockedCells
End Sub