Try one of the methods from this thread:
http://groups.google.com.au/group/mi...0d906f1d1bf80f
HTH.

"KateB" wrote:

Just a quick question, i'm trying to graph some data, for which I've
used a x-y scatter chart. So far, so good, the data represents an
average value for a a 1/2 day period.

The chart interpolates between my points, instead of displaying
stepwise data, with the value displayed being the average for the next
period (until the new point).

I can't for love nor money find an option in the charts to do this -
am I missing something??

Hope this makes sense, let me know if I can post a picture somwhere!

Thanks!
Kate