Option Explicit
 
Private Type MinMax
  Min As Single
  Max As Single
End Type

Public Sub Import()
  
  Dim rngTarget As Excel.Range
  Dim vntFilenames As Variant
  Dim vntFilename As Variant
  
  vntFilenames = Application.GetOpenFilename("Textdatei (*.txt),*.txt", Title:="Messdatei auswerten", MultiSelect:=True)
  If VarType(vntFilename) = vbBoolean Then Exit Sub
  
  For Each vntFilename In vntFilenames
    With ThisWorkbook.Worksheets.Add()
      .Name = Right$(vntFilename, Len(vntFilename) - InStrRev(vntFilename, "\"))
      Set rngTarget = .Range("A1")
    End With
    Call ImportFromFile(CStr(vntFilename), rngTarget)
  Next
  
End Sub

Public Sub ImportFromFile(Filename As String, Target As Excel.Range)
  
  Call Workbooks.OpenText( _
          Filename:=Filename, _
          ConsecutiveDelimiter:=True, _
          Semicolon:=True)
   
  Dim rngData   As Excel.Range
  Dim rngMass   As Excel.Range
  Dim rngSpeed  As Excel.Range
  Dim udtMass   As MinMax
  Dim udtSpeed  As MinMax
  Dim nOK       As Long
  Dim i         As Long
   
  With ActiveWorkbook.Worksheets(1)
     
    udtMass.Min = .Range("B3").Value + .Range("B4").Value 'value ist neg.
    udtMass.Max = .Range("B3").Value + .Range("B5").Value
     
    udtSpeed.Min = .Range("B7").Value + .Range("B8").Value 'value ist neg.
    udtSpeed.Max = .Range("B7").Value + .Range("B9").Value
     
    'Datenbereich
    'in 1. Spalte steht das Gewicht
    'in 2. Spalte steht die Geschwindigkeit
    Set rngData = .Range("A14", .Cells.SpecialCells(XlCellType.xlCellTypeLastCell))
     
  End With
   
  For i = 1 To rngData.Rows.Count
     
    Set rngMass = rngData.Cells(i, 1)
    Set rngSpeed = rngData.Cells(i, 2)
     
    If (udtMass.Min <= rngMass.Value And rngMass.Value <= udtMass.Max Or rngMass.Value = "") _
    And (udtSpeed.Min <= rngSpeed.Value And rngSpeed.Value <= udtSpeed.Max Or rngSpeed.Value = "") _
    Then
      nOK = nOK + 1
    End If
     
  Next
  
  Target.Cells(1, 1).Value = "Anzahl Messungen:"
  Target.Cells(1, 2).Value = rngData.Rows.Count
  Target.Cells(2, 1).Value = "OK:"
  Target.Cells(2, 2).Value = nOK
  Target.Cells(3, 1).Value = "Nicht ok:"
  Target.Cells(3, 2).Value = rngData.Rows.Count - nOK
  Target.Resize(, 2).EntireColumn.AutoFit
  
  Call rngData.Worksheet.Parent.Close(SaveChanges:=False)
  
  Set Target = Target.Offset(3)
  
End Sub

Alternativ könnte man sich die ermittelten Werte auch zurückgeben lassen und außerhalb der Sub ImportFromFile wohin schreiben.

Grüße