Runtime Error 481 Invalid Picture

hello,

iīve a very big Problem to view a diagram in a userform. i get always the error runtime error 481 invalid Picture and i didnīt find any solution.
maybe you can help me.

Iīve a userform and a makro

here is the makro code

when i click on the degugg button the following code will be Show in yellow

UserForm8.Image1.Picture = LoadPicture(dateiname)

Sub Bild_Anzeigen(strTab As String, strDia As String)
         ActiveSheet.Unprotect Password:="test"
             Dim Diagramm As Object
             Dim dblBreite As Double
             Dim dblHoehe As Double
             Set Diagramm = Worksheets(strTab).ChartObjects(strDia).Chart
             With Diagramm.Parent
               dblHoehe = .Height
               dblBreite = .Width
               .Height = dblHoehe
               .Width = dblBreite
               Dateiname = ThisWorkbook.Path & Application.PathSeparator & "diagramm.bmp"
             End With
             Diagramm.Export Filename:=Dateiname, FilterName:="bmp"
             With UserForm8
               .Image1.Width = Diagramm.Parent.Width
               .Image1.Height = Diagramm.Parent.Height
               .Width = .Image1.Width + 15
               .Height = .Image1.Height + 30
             End With
             UserForm8.Image1.Picture = LoadPicture(Dateiname)
             With Diagramm.Parent
               .Height = Diagramm.Parent.Height
               .Width = Diagramm.Parent.Width
             End With
             Kill Dateiname
             UserForm8.Show
             ActiveSheet.Protect Password:="test", DrawingObjects:=False, Contents:=True, Scenarios:= _
                 True, AllowFiltering:=True
         End Sub

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