I used a label inside my snippet just to test it; but this will simply increment and decrement a float value by 0.2f between the values specified in the conditionals. I have it updating between 8f and 15f. Must be run on a timer (make sure the interval is low "ex: mine is on 1ms"). It's still a little buggy and by buggy I mean it bugs me that it's jerky. It's not smooth transition.
I fixed the jerky bug inside of the source.
//Line 35 FontSize += 0.25f; //Line 44 FontSize -= 0.25f;
Yes this will work with anything that has a font. Just simply change it from a label.
textBox1.Font = new Font("OCR A Extended", FontSize, FontStyle.Regular, GraphicsUnit.Point, ((byte)(0));
Most of use don't know the exact font names so just change your text to the font you want, then go into the designer source of the form and get the value from the font assignment in there.
Jamie - Studio 41 Games (Owner/Head Developer)