Hide Minus Values On Y-axis On A Chart

column chart displaying various pieces of data.

At the top of my worksheet I have a combo box which allows you to select a local authority name; and all relevant information in the worksheet is highlighted (using conditional formatting, extra series in charts to make relevant points highlight in red, etc).

I've added a series to the chart and changed it's type to line - then with the data labels positioned beneath the points on the line I can get conditional formatted x category labels - all outlined here: [url]

Because my x category labels are fairly long I've had to give them an orientation of -90 and make the minimum y-axis value equal to -200 to give enough room beneath the chart to fit the text in.

As I said above, the values below 0 are just there to provide space at the bottom of the chart, so my question is: is there a way to hide these negative values? I'm sure I've done it before, but can't remember how - I thought maybe a custom number format of #;[White]# would work, but it just inverted my text (white text on black background).