Problems with Vba to save file & convert to PDF

Update - The problem appears to be with saving to C:\ because if i change this to D:\ it works fine. Is there a way that i can have a single pop up box or window to specify the save location for both the .xlsm & pdf versions of the file each time?

Update 2 - I have got it partly working using an ActiveX button and the below code however there is a problem if i press 'Cancel' to the file browser window when saving. I first get the following message 'A file named 'FALSE.xlsm' already exists in this location. Do you want to replace it?'

If i press No or Cancel I thenget Run-time error '1004' at line 'ThisWorkbook.SaveAs thefilename'

Private Sub CommandButton2_Click()

ActiveSheet.Unprotect "password"
Sheet1.Range("c10").FormulaR1C1 = "=IF(RC[8]=0,"""",NOW())"
ActiveSheet.Protect "password"
ThisFile = Sheets("Header").Range("c20").Value
thefilename = Application.GetSaveAsFilename _
(ThisFile, filefilter:="Excel Files, *.xlsm")
ThisWorkbook.SaveAs thefilename
ThisFile = Sheets("Header").Range("c20").Value
thefilename = Application.GetSaveAsFilename _
(ThisFile, filefilter:="PDF Files, *.pdf")
ThisWorkbook.SaveAs thefilename
Application.Quit
End Sub

Update 3 - I think i have cracked it with the following code. It isn't pretty but it appears to work.

Sub sbSaveExcelDialog()

Dim sFileSaveName As Variant
ActiveSheet.Unprotect "password"
Sheet1.Range("c10").FormulaR1C1 = "=IF(RC[8]=0,"""",NOW())"
ActiveSheet.Protect "password"
ThisFile = Sheets("Header").Range("c20").Value
sFileSaveName = Application.GetSaveAsFilename _
(ThisFile, fileFilter:="Excel Files, *.xlsm")
If sFileSaveName <> False Then
ActiveWorkbook.SaveAs sFileSaveName
End If
ThisFile = Sheets("Header").Range("c20").Value
sFileSaveName = Application.GetSaveAsFilename _
(ThisFile, fileFilter:="PDF Files, *.pdf")
If sFileSaveName <> False Then
ActiveWorkbook.SaveAs sFileSaveName
Application.Quit
End If

End Sub