Hi Dan,
Please follow the following procedure to achieve ur goal
1. Open Excel
2. Goto Tools -> Macros -> Visual Basic Editor, it open VB editor.
3. Double click Sheet1 in left pane to open code workspace.
4. Copy & paste this code in sheet1 worspace. I wrote this for sheet1
Private Sub worksheet_change(ByVal Target As Range)
Dim varG2 As Integer
Dim varH2 As Integer
Dim varPercentage As Integer
varH2 = Sheet1.Range("H2")
varG2 = Sheet1.Range("G2")
varPercentage = (varH2 / varG2) * 100
If varPercentage = 0 Then
Sheet1.Range("H2").Interior.Color = vbGreen
ElseIf varPercentage > 0 And varPercentage < 11 Then
Sheet1.Range("H2").Interior.Color = vbYellow
ElseIf varPercentage > 10 Then
Sheet1.Range("H2").Interior.Color = vbRed
End If
End Sub
5. Save it.
Please find the example attached below
Conditional Formatting.zip