Changing text in textbox once something is erased

[paralinx]

Hi all,

I'm making a Notetaking program that makes it faster for writing notes on the computer. It will add Roman Numerals and Upper Case Letters, Lower Case, ect.

However, my problem is when I put say three roman numerals into the textbox

I.

II.

III.

And I erase all three, and put anothe roman numeral in, it will put roman numeral four in (IV) How could I make it so it checks to see what roman numeral is in the textbox and then enters the next one up?

So if I have I. II. III. in the textbox and erase II. and III. it will enter a II.

Sorry if you have a hard time understand this

I have also attached my project so you can maybe take a look at it