Adding values to AD fields via Powershell

Hi Guys

I would like some help with something i am trying to achieve. Basically I will like to have a script which will check the value on the Telephone Number field of an AD user and then add the extension ( last 4 digit of the telephone number value ) to the IP Phone Number (Other) Field.

Ideally this operation requires to take place for only the user accounts that are enabled in the OU.

Any Help will be highly appreciated.

Thank you.

R