> Now, how can I go back and change all the textboxes on my forms
> to use this class?

Time to play! While there are tools available to do this, sometimes it helps just to go in to the file and see how it works. For example,

For example, if you created a modified textbox called myTxt, and put it in classlib.vcx:

Use [my.scx|my.vcx] alias 'my'
UPDATE 'my' SET class = 'myTxt', classloc = 'classlib.vcx' ;
WHERE classname = 'textbox'
Use in 'my'

Extremely dangerous! Also extremely cool to see it work! Have fun.