There is no check box in the format toolbar unless you've customized your
toolbars. There are two types of check boxes.
If it is from the Forms toolbar, you can't change the font without some
coding (I think!). You can tell if it is from the forms toolbar if you right
click and there is no properties option in the right-click menu.
If it is from the Control Toolbox menu, you can right click and choose
properties. double click on font and you can change the font size and make
it bold.