Combo Box Macro In Worksheet Doesn't Run Automatically

I have a combo box in a worksheet with a macro written for it that works fine but when I open the worksheet it doesn't run automatically, I have to find the macro and tell it to run.

How can I get it to run as soon as the worksheet is opened

Here is the code for the macro


Private Sub combobox()

ComboBox1.clear
ComboBox1.AddItem "Mit Rekuperator"
ComboBox1.AddItem "Ohne Rekuperator"

End Sub

Private Sub ComboBox1_Change()

Run "PinchInternHeatExchanger"
Select Case ComboBox1.Text
Case "Mit Rekuperator"
ActiveSheet.Range("I62") = Worksheets("uorc").Range("L99")
Case "Ohne Rekuperator"
ActiveSheet.Range("I62") = Worksheets("uorc").Range("E11")
End Select
Run "PinchPoint"
End Sub