First text box in form not working right

[Jack]

I have a form with three text boxes each initialized with an integer. No
problem. When the program is running I type in the first text box (which
has the number 12 which is also not highlighted) the number 25 and press
enter. Instead of showing 25 the text box shows 1225. Everything works as
it should when I type into the remaining text boxes i.e.. I get a
highlighted number which is overwritten by the number I typed in.

How can I fix this? What is happening?

 

[Tom Ogilvy]

if this is the situation when the form is shown, set the tabindex property
of the first textbox to 0, the second textbox to 1 and the third textbox to
2.