You could change the font size an the font.
But changes in the XML-source is not so good. Better is the scripteditor (you will find them under "window" | Scripteditor
For example when you click a checkbox.
Copy the following script in the change-event of the checkbox
if(this.rawValue == 1)
{
ObjectName.font.typeface = "Times New Roman";
ObjectName.font.size = "6pt";
}else
{
ObjectName.font.typeface = "Courier";
ObjectName.font.size = "13pt";
}
Hope it's helpull?
Mandy