Chart in userform

Hi Guys,

I'm trying to display the chart in userform using the code below which i found on net, but getting an error on red line below stating that the variable not set, any ideas why it is happening?

Any thoughts are welcome, thanks in advance.

Private Sub UserForm_Initialize()
Dim ChartNum As Integer
  ChartNum = 1
    UpdateChart
End sub

Private Sub UpdateChart()
Dim ChartNum As Integer
    Set CurrentChart = Sheets("Data Collection").ChartObjects(ChartNum).Chart
    CurrentChart.Parent.Width = 300
    CurrentChart.Parent.Height = 150

'   Save chart as GIF
    Fname = ThisWorkbook.Path & Application.PathSeparator & "temp.gif"
    CurrentChart.Export Filename:=Fname, FilterName:="GIF"

'   Show the chart
    Image1.Picture = LoadPicture(Fname)
End Sub