For i = 3 To 300
x = 0
j = i - 1
If Cells(i, 2).Value = "FX" And Not IsEmpty(Cells(i - 1, 1).Value) Then
Do While Cells(j, 4).Value <> ""
x = Cells(j, 4).Value + x
j = j - 1
Loop
End If
Cells(i, 4).vlue = x
Next i