You sure can! It is easy. Understanding the symbol code (<MOD-DIA> = Ø) and Variables (<hw-diam> = Diameter, is the hard part.
First, what is a Hole Callout? Hole Callout is information from the Hole Wizard or circular extrude cut. Such as description, diameter size, depth, quantity. You get the gist. I always use the Hole Wizard, even if it is just a hole. That way you do not have to manually enter the quantity.
The default format file for the Hole Wizard types is located here:
You will find two files:
The first file is calloutformat.txt and a second file, calloutformat_2.txt which is a simplified version. SOLIDWORKS uses the first file as the active file. If you wanted to use the second file, you would have the rename the files.
Let us look at part of the text file. It can look intimidating (like Global Variables when I first started working with them). Once you understand it, you should be good to go.
The text file will break it down into Standards (ANSI INCH, ANSI METRIC, BSI, DIN and so on and so forth). It also breaks it down by Hole Types with the different options to choose from. With each option you have different Variables.
Depending on what your options are will determine what will show up on the drawing. To place a hole callout on your drawing, click Hole callout 
and select the hole. The drawing now has the callout and if you edit the Hole Wizard feature in the model, the callout updates automatically.
Here is what you have been waiting for. Modifying the calloutformat.txt file. You must have Admin rights to make these changes. You will also need to exit out of SOLIDWORKS before making the changes.
I will change the hole callout for the counterbore. I will change the counterbore symbol 
(<HOLE-SPOT>) to read C’BORE, the counterbore depth symbol 
(<HOLE-DEPTH>) to read DEPTH.
From this in the text file:
To this:
I will also change the Tapped hole callout. Rather than the description and class ¼-20 UNC (<hw-threaddesc> <hw-threadclass>), I will change it to just the size ¼-20 (<hw-threadsize>).
From This in the text file:
To this:
These changes will now apply to any drawing you create moving forward.
You can view and change the hole callout Variables in the drawing as well. However, this is specific to the drawing. Click on the Hole Callout Annotation and in the Property Manager under Dimension Text, BAM there it is. You can manually type the Variable or choose from a pull-down list.
You can manually type the Variable or choose from a pull-down list. Clicking Callout Variables will bring up the list.
I almost forgot! If you scroll all the way to the bottom of the calloutformat file you will find all the Variables and their Descriptions.
Hole Wizard variables are in lower case letters & are enclosed in braces, they have the form: <hw-type>. Items in capital letters & enclosed in braces, are SolidWorks symbol names, they have the form: <MOD-DIA>. Here is a part of the list.
Stay safe and have blessed day.
Roger G. Ruffin
Senior Application Engineer
Computer Aided Technology, Inc.
