Put the cursor at the end of the number, press MenuKey > Add Pause (repeat if necessary) > add extension number. You can also select "Add Wait", which will prompt you before dialing the extension. I think a pause is two seconds, so add as many as needed until the phone system is ready to accept the extension.
Posted from my CrackBerry at wapforums.crackberry.com
CrackBerry is in no way Affiliated with BlackBerry. We take pride in our unbiased content, however do occasionally receive free products from vendors that we review or discuss. For more info click here.