Run time Error 424 object required - public key encryption macro - excel

Question

We are currently trying to get the encryption macro to work on multiple cells throughout the workbook, I have a lot going on with some of these cells so I am open to anything to make this flow better. Currently, the macro is under our finalize form button. This is the coding on sheet 1, the function code is under "this workbook"
When we try running this under other worksheet_selectionchange(ByVal target As Range) code, it doesn't allow the text box (got_focus) code to run on the cell.
I've tried changing the location of the code whether its in its own sub or being called to with a button and I'm unable to get this to correct itself. the cell that is in range is merged and would be ("B23:D23"), but making that change didn't change my debug error.
Private Sub FINALIZEBTN_Click()
Dim response As VbMsgBoxResult
response = MsgBox("Have you completed the form in full?", vbYesNo)
If response = vbYes Then
MsgBox "Do not forget to save and submit this form"
ElseIf response = vbNo Then
MsgBox "Please review and complete the form in full"
Exit Sub
End If
Dim searchRange As Excel.Range
Dim cell As Variant
Dim RegEx As Object
Set RegEx = CreateObject("VBScript.RegExp")
With RegEx
.Pattern = "[^ :#a-zA-Z0-9&\-]+"
.Global = True
.MultiLine = True
End With
Set searchRange = ActiveSheet.Range("B18:E52") '// Change as required
For Each cell In searchRange.Cells
If RegEx.Test(cell) Then cell.value = RegEx.Replace(cell.value, "")
cell.value = UCase(cell.value)
Next cell
Set searchRange = Nothing
Set RegEx = Nothing
'ENCRYPTION MACRO
Dim KeyCells As Range
Set KeyCells = Range("B23")
Dim publicKey As String
publicKey = "<RSAKeyValue><Modulus>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</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>" 'put entire xml string here
If Not Application.Intersect(KeyCells, Range(target.Address)) Is Nothing Then
Application.EnableEvents = False
If VarType(Range(target.Address).value) <> 8204 Then
If Len(Range(target.Address).value) < 256 Then 'making sure that encry sting isnt previously encrypted
Range(target.Address).value = ThisWorkbook.Encrypt(publicKey, CStr(Range(target.Address).value))
Range(target.Address).HorizontalAlignment = -4108 'XLALIGNCENTER
End If
Else
Range(target.Address).HorizontalAlignment = -4131 'XLALIGNLEFT
End If
Application.EnableEvents = True
End If
End Sub
The line
If Not Application.Intersect(KeyCells, Range(target.Address)) Is Nothing Then causes the run-time error 424 object required pop up.