Waterfall chart problem

Hi,
I am having trouble with a waterfall graph. I have tried following the instructions on

HTML Code: 

for the chart which has Stacked Columns for Positive and Negative Data but I couldn't get it to work.

Can anyone who has experience of these charts please take a look at my data – ignore the chart as I know that will be wrong. I think it’s a problem with the blank column

Paul

Can anyone help please?