Macro Code Will Not Stop Saving In My Module

So I am Very New with Macros. Any Help would be appreciated. I have a code That I am running in my Module. It is designed to Stop Everything (ie Invoice Register, Todays Date, Saving) Unless All Specific Cells Are filled. I have managed to splice together a code that opens a message window and higlights the blank cells. It still However continues with the rest of my Macro Including Saving. This My Complete Module Code:

Sub fullmacsro()
    FillCells
    TodaysDate
    PostToRegister
    SavePdf
    SaveXLMFile
    NextInvoice
   
End Sub

Sub FillCells()

    Dim Start As Boolean
    Dim Rng1 As Range, Rng3 As Range, Rng4 As Range
     
    Dim Prompt As String, RngStr As String
    Dim Cell As Range
     'set your ranges here
     'Rng1 is on sheet "Group Profile" and cells B5 through B14
     'Cell F1, A range of F5 through F7 etc.  you can change these to
     'suit your needs.
    Set Rng1 = Sheets("1 Invoice Notes").Range("B4,B8,B9,B10,B14,B15,B17,B29,B30,B31,B32,D8,D9,F30,F31,J37")
         'message is returned if there are blank cells
    Prompt = "Please check your data ensuring all required " & _
    "cells are complete." & vbCrLf & "you will not be able " & _
    "to close or save the workbook until the form has been filled " & _
    "out completely. " & vbCrLf & vbCrLf & _
    "The following cells are incomplete and have been highlighted yellow:" _
    & vbCrLf & vbCrLf
    Start = True
     'highlights the blank cells
    For Each Cell In Rng1
        If Cell.Value = vbNullString Then
            Cell.Interior.ColorIndex = 6 '** color yellow
            If Start Then RngStr = RngStr & Cell.Parent.Name & vbCrLf
            Start = False
            RngStr = RngStr & Cell.Address(False, False) & ", "
        Else
            Cell.Interior.ColorIndex = 0 '** no color
        End If
    Next
    If RngStr <> "" Then RngStr = Left$(RngStr, Len(RngStr) - 2)
    Start = True
    If RngStr <> "" Then RngStr = RngStr & vbCrLf & vbCrLf
   
    If RngStr <> "" Then RngStr = Left$(RngStr, Len(RngStr) - 2)
    Start = True
    If RngStr <> "" Then RngStr = RngStr & vbCrLf & vbCrLf
   
      If RngStr <> "" Then RngStr = Left$(RngStr, Len(RngStr) - 2)
    If RngStr <> "" Then
        MsgBox Prompt & RngStr, vbCritical, "Incomplete Data"
        Cancel = True
    Else
         'saves the changes before closing
        ThisWorkbook.Save
        Cancel = False
    End If
     
    Set Rng1 = Nothing
    Set Rng3 = Nothing
    Set Rng4 = Nothing
     
End Sub

Sub TodaysDate()
Range("B6").Value = Format(Now(), "MM/DD/YYYY")
End Sub

Sub PostToRegister()
    Dim WS1 As Worksheet
    Dim WS4 As Worksheet
    Set WS1 = Worksheets("1 Invoice Notes")
    Set WS4 = Worksheets("4 Register")
    ' Figure out which Row Is next
    NextRow = WS4.Cells(Rows.Count, 1).End(xlUp).Row + 1
    ' Write the important Values To Register Last Number is How many items
    WS4.Cells(NextRow, 1).Resize(1, 7).Resize(1, 7).Value = Array(WS1.Range("B6"), WS1.Range("D6"), WS1.Range("B8"), WS1.Range("J37"), WS1.Range("J36"), WS1.Range("i33"), WS1.Range("J38"))
    
End Sub

Sub SavePdf()

'This macro opens the SaveAs option with the defult file path "you have to set this file path below" coverts the whole sheet into .pdf file format
'And opens the .pdf to view <-- you can disable the view after covert option with lower code: OpenAfterPublish:=False

    pdfName = Sheet2.Range("D6") & Sheet2.Range("B8") & Sheet2.Range("D8")
    ChDir "C:\Users\Terrance\Dropbox\Marks Custom Drywall And Finishing\3 INVOICING DEPOSITS\4 outstanding invoice"
    fileSaveName = Application.GetSaveAsFilename(pdfName, _
    fileFilter:="PDF Files (*.pdf), *.pdf")
    If fileSaveName <> False Then
    Sheet2.ExportAsFixedFormat Type:=xlTypePDF, Filename:= _
        fileSaveName _
        , Quality:=xlQualityStandard, IncludeDocProperties:=True, IgnorePrintAreas _
        :=False, OpenAfterPublish:=True
    End If
    MsgBox "File Saved to" & " " & fileSaveName
    
    End Sub
    
    Sub SaveXLMFile()
    
    
    
    Dim NewFN As Variant
    
    ActiveSheet.Copy
    NewFN = "C:\Users\Terrance\Dropbox\Marks Custom Drywall And Finishing\3 INVOICING DEPOSITS\6 Invoice Copy\" & Range("D6").Value & Range("B8").Value & Range("D8").Value & ".xlsx"
    ActiveWorkbook.SaveAs NewFN, xlOpenXMLWorkbook
    ActiveWorkbook.Close
    
    
    
       End Sub
       
       Sub NextInvoice()
    
           
     
    Range("D6").Value = Range("D6").Value + 1
    Range("B8:B15").ClearContents
    Range("D8:J9").ClearContents
    Range("B17:B20").ClearContents
    Range("D12:E29").ClearContents
    Range("F12:G12").ClearContents
    Range("F15:G15").ClearContents
    Range("F18:G18").ClearContents
    Range("F21:G21").ClearContents
    Range("F24:G24").ClearContents
    Range("F27:G27").ClearContents
    Range("B4:H4").ClearContents
    Range("B29:B35").ClearContents
    Range("J37").ClearContents
    Range("F30").ClearContents
    Range("F31").ClearContents
    
End Sub

Thank you in advance. Any Help would be appreciated