Calculate & Store using Excel 2007 vba

[jkashi]

I am trying to find the percentage of the value from cell (8,4) and store the result in cell (9,4). I am getting "Runtime Error 424" Object required.
Here is my code.

Sub SubmitDP()

Dim r1, r2, r3 As Integer

Set r1 = thisworksheet.Sheets("Sheet1").Cells(8, 4).Value
Set r2 = thisworksheet.Sheets("Sheet1").Cells(9, 4).Value

r2.Value = r1.Value * 0.15

End Sub