Not process the saving invoice & never go to the next unless complete specific cell

[DIMI]

Good evening
I have two problems with the following billing code: 1) I have configured it to store a copy on the hard drive but when I go and find the file I can edit it I do not want to be done. I still want to protect the excel sheet from changes But I can see it or save it as pdf, and 2) I would not let me save it and send me a message if it's not in the F16, E31, G31 cells.

Thank you.

Sub NextInvoice()
Range("I5").Value = Range("I5").Value + 1
Range("G26").Value = Range("G34")
Range("G30").Value = Range("G34")
Range("G31").MergeArea.ClearContents
Range("G34").MergeArea.ClearContents
Range("G38").MergeArea.ClearContents
Range("E31").MergeArea.ClearContents
Range("G34").Formula = "=G30-G31"

End Sub

Sub PostToRegister()
Dim Lrow As Long
Lrow = Sheets("list invoice").Cells(Rows.Count, 1).End(xlUp).Row
Dim inDate As Date, inNum As Long
inDate = Sheets("invoice").Cells(38, 7).Value
inNum = Sheets("invoice").Cells(5, 9).Value
Dim exDate, exNum As Long


exDate = Sheets("list invoice").Cells(Lrow, 1).Value
exNum = Sheets("list invoice").Cells(Lrow, 2).Value
If inDate >= exDate And inNum > exNum Then
Dim WS1 As Worksheet
Dim WS2 As Worksheet
Set WS1 = Worksheets("invoice")
Set WS2 = Worksheets("list invoice")
'Figure out which row is the next row
NextRow = WS2.Cells(Rows.Count, 1).End(xlUp).Row + 1

'Write the important values to Register
'Write the important values to Register
WS2.Cells(NextRow, 1).Resize(1, 6).Value = Array(WS1.Range("G38"), WS1.Range("I5"), WS1.Range("H5"), _
WS1.Range("F16"), WS1.Range("G31"), WS1.Range("E31"))

Else
MsgBox "error."
End
End If
End Sub

Sub SaveInvWithNewName()

Dim NewFN
Dim variable1
Dim variable2

With ActiveSheet
variable1 = .Range("A32").Value
variable2 = .Range("A35").Value
.Copy
End With

With ActiveSheet
.Range("A32").Value = variable1
.Range("A35").Value = variable2
End With

With ActiveSheet
NewFN = "C:\invoice\" & Range("I5").Value & Range("H5").Value & Range("I49").Value & Range("F16").Value & ".xlsx"
ActiveSheet.SaveAs NewFN, FileFormat:=xlOpenXMLWorkbook
Application.DisplayAlerts = True
ActiveWorkbook.PrintOut From:=1, To:=1, copies:=2
ActiveWorkbook.Close SaveChanges:=False
NextInvoice
End With
End Sub

Sub FINISH()
Call PostToRegister
Call SaveInvWithNewName
End Sub