If you need to scale box charts separately then you should first extract the individual box charts to separate layers. There is a tool on the Graph toolbar that does exactly this : "Extract to Layers". It will popup a dialog asking for number of rows and columns. Enter 1 Row and the number of columns equal to the number of box charts. Click OK to this and the next dialog.
Now open the script window and execute this script:
doc -e LW {
sum(%C);
y1=sum.min;y2=sum.max;
x1=.5;x2=1.5;
layer.y.rescale=1;
}
(Execute the script by selecting the text in the Script Window and pressing Enter.)
The script sets the Y axis scale for each box chart to the minimum and maximum values of the original dataset and sets the scale mode to 'manual'. If you have other requirements, review the STAT object or the percentile function in the LabTalk Manual.