SOLVED; Chart doesn't update fast enough to show incremental change in values

I'm using a 3d bar chart. I want to show the movement of a value from one cell to another for clarity. I currently have something like this:

Range("$a$1").value = 5
Range("$a$2").value = 0
count=0
Do Until count = 50
Range("$a$1").value = Range("$a$1").value - 0.1
Range("$a$2").value = Range("$a$2").value + 0.1
count = count + 1
'Perhaps some refresh chart code goes here?
Loop

But the chart doesn't update until after the change. Can anyone point me in the right direction here?