Graphing

Is there any way to have the data series on a graph changing so that it only goes to a certain value. For example, i have a data series that changes when i change the input data, and the graph updates to reflect this and ive set the miimum on the y-axes to 0 so it wont graph below zero. But the graph stays big and the trendline just moves into the corner until i change the data series.

Is there anyway i can have the data series update itself to only go to where the value reaches 0?!

If that makes sense :P