File name without file path (data import) - Excel crash

Hi, I've got the following Import macro, that imports data from another Excel file:

Sub Import()

Dim File As Variant
Dim Filename As Variant
Dim Master As Variant

MsgBox "Choose file", vbOKOnly
File = Application.GetOpenFilename("Excel files (*.xls),*.xls", , "Open an Excel file...")

If Not File = False Then Workbooks.Open (File)

Master = ThisWorkbook.Name

    Filename = Right(File, 20)
  
    Sheets(1).Activate
    Range("G11").Select
    Selection.Copy
    Windows(Master).Activate
    Range("G11").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Windows(Filename).Activate

    Range("G19").Select
    Selection.Copy
    Windows(Master).Activate
    Range("G19").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Windows(Filename).Activate

    ActiveWorkbook.Close False
   
    MsgBox "Import completed"
    
End Sub

Everything works fine as long as the file name consists of 20 (or whatever number we will put there) signs (including .xls) due to this line Filename = Right(File, 20).

Is there a way to change the code in a way that it will just get the file name without specifying its exact number of signs?

Thanks in advance!

After finding solution to the file name problem, I'm now encountering a problem with crashes.. After using this macro for several times (5-6) Excel 2010 crashes.
Do you have any idea what might be causing this or what to change in the code to prevent those crashes?

The code:

Sub Import3()

Dim File As Variant
Dim Master As Variant
MsgBox "Choose file", vbOKOnly
File = Application.GetOpenFilename("Excel files (*.xls),*.xls", , "Open an Excel file...")
File = Mid(File, InStrRev(File, "\") + 1)

If Not File = False Then Workbooks.Open (File)
Master = ThisWorkbook.Name

    Sheets(1).Activate
    Range("G13").Select
    Selection.Copy
    Windows(Master).Activate
    Range("G13").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Windows(File).Activate

    Range("G18").Select
    Selection.Copy
    Windows(Master).Activate
    Range("G18").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Windows(File).Activate

    ActiveWorkbook.Close True

    MsgBox "Import completed"
    
End Sub