Subtract range from cell until zero or negative

I am trying to write a code that will take a value from column H and sequentially subtract the values from I to Q until the value is at or below zero and then stop, and populate column G with the value. Also i would have an output that specifies how far into the range it got.

G H I J K L M N O P Q
2000 1100 850 650 100 0 0 0 0 0
5000 350 1200 1500 2010 2000 1900 1750 1650 1550

Here's what i have so far, but i cant figure out how to get it to loop correctly, it currently only subtract the first value in column I

Dim k As Integer, l As Integer
For k = 4 To 20000
    Select Case Cells(k, "H").Value
    Case Is > 0
        l = 9
        Cells(k, "G") = (Cells(k, "H").Value - Cells(k, l).Value)
        l = l + 1
    Case Is =< 0
    End Select
Next k

Thanks