Keep Text in Uppercase

I am using Adobe Acrobat 9 Standard. I have script to change lowercase to uppercase in many form fields on a PDF. But if I return to the field that has already changed lowercase to uppercase, it goes back to lowercase until I exit the field again. These fields are used a lot to copy and paste into other applications and I want the fields to remain in uppercase once they are converted.

Please help!

I am using this to convert to uppercase: event.value = event.value.toUpperCase();

Thanks,

Brandy