How to limit to enter a IP address in TextField?

Hello everyone,

I have a PDF form which users need to enter a IP address. In order to get a correct IP address, I need to limit a TextField's pattern.

What my boss want me to realize is like the picture below:

It means when users fill 3 numbers of IP address, it will jump to next place and display a point "." automatically.

But I found it can't change the rawvalue of the TextField when it is in a typing status(in Change event).

Do you think if I can realize this requirement? How can I do ?

Thanks a lot!

Elly