Save worksheet as seperate workbook problem- File name issue

I am using the following code attached to a button to save the worksheet as a seperate workbook. The problem I have is if I try to use a range for the filename then the code crashes! Should be simple but cant get it to work?

Sub Save_ActiveSheet_NoCode()
'Working in 97-2010
    Dim FileExtStr As String
    Dim FileFormatNum As Long
    Dim Sourcewb As Workbook
    Dim Destwb As Workbook
    Dim FilePath As String
    Dim FileName As String
    Dim I As Long

    With Application
        .ScreenUpdating = False
        .EnableEvents = False
    End With

    Set Sourcewb = ActiveWorkbook

    'Copy the sheet to a new workbook
    ActiveSheet.Copy
    Set Destwb = ActiveWorkbook

    'Determine the Excel version and file extension/format
    With Destwb
        If Val(Application.Version) < 12 Then
            'You use Excel 97-2003
            FileExtStr = ".xls": FileFormatNum = -4143
        Else
            'You use Excel 2007-2010, we exit the sub when your answer is
            'NO in the security dialog that you only see  when you copy
            'an sheet from a xlsm file with macro's disabled.
            If Sourcewb.Name = .Name Then
                With Application
                    .ScreenUpdating = True
                    .EnableEvents = True
                End With
                MsgBox "Your answer is NO in the security dialog"
                Exit Sub
            Else
                Select Case Sourcewb.FileFormat
                Case 51: FileExtStr = ".xlsx": FileFormatNum = 51
                Case 52:
                    If .HasVBProject Then
                        FileExtStr = ".xlsm": FileFormatNum = 52
                    Else
                        FileExtStr = ".xlsx": FileFormatNum = 51
                    End If
                Case 56: FileExtStr = ".xls": FileFormatNum = 56
                Case Else: FileExtStr = ".xlsb": FileFormatNum = 50
                End Select
            End If
        End If
    End With

    '    'Change all cells in the worksheet to values if you want
        With Destwb.Sheets(1).UsedRange
            .Cells.Copy
            .Cells.PasteSpecial xlPasteValues
            .Cells(1).Select
        End With
        Application.CutCopyMode = False
        
        
 Dim shp As Shape
 Dim myVar As Shapes
 
ActiveSheet.Activate
 Count = ActiveSheet.Shapes.Count
 
'Set myVar = Sheets(ActiveSheet.Name).Shapes
 For I = Count To 1 Step -1
 ActiveSheet.Shapes(I).Delete 'myVar(i).Delete
 Next I
 
            

    'Save the new workbook
    FilePath = "C:\Folder Name\Folder Name\"
    FileName = "File Name"

    With Destwb
        .SaveAs FilePath & FileName & FileExtStr, _
                FileFormat:=FileFormatNum
        On Error Resume Next
      
        On Error GoTo 0
        .Close SaveChanges:=True
    End With

 

    With Application
        .ScreenUpdating = True
        .EnableEvents = True
    End With
End Sub

If I replace this line:

FileName = "File Name"

with this line I thought it would be that simple?

FileName = Range ("B3").Value

But then it doesnt seem to like this:

.SaveAs FilePath & FileName & FileExtStr, _
                FileFormat:=FileFormatNum

would be nice if I could also add the date and time to the file name so multiple copies can be saved without overwriting, is this possible?
Hopfully someone can help me
Thanks
Andrew