OK I'm not sure how your system will work so perhaps we can do a little test. This is not really answering your questions, but if it works I know the approach is broadly correct and if it doesn't work it will need a re-think.
Can you paste this code into the sheet module (right-click the sheet tab, View Code and paste):
Private Sub Worksheet_Calculate()
If Range("A1").Value = 1 Then
Range("E2").Value = WorksheetFunction.Max(Range("B2:B10"))
End If
End Sub
When the sheet calculates, if A1=1 it should just put the max of B2:B10 in E2.
Let me know how you get on.
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EDIT: if that doesn't work, can you try this code in the module of sheet "7" and see if it runs whenever I2 is changed.
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$I$2" Then
With Worksheets("H019")
If .Range("A1").Value = 1 Then
.Range("E2").Value = WorksheetFunction.Max(.Range("B2:B10"))
End If
End With
End If
End Sub
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