You could use a macro like the following in the worksheet's code module:
Code:
Private Sub Worksheet_Calculate()
Application.Calculation = xlCalculationManual
If Range("A10").Value < 0.1 Then
Range("b10").Value = Range("b10").Value + 1
End If
End Sub
Note that the code sets the Calculation mode to Manual. That's necessary to stop the update forcing another re-calc. It also means you'll need to manually re-set the calculation mode when you're done.