Suppress dial tone - Promted user and then connect instead?

I followed Ned Vittles article on setting up DISA.

exten => 4,1,Authenticate(1234588)
exten => 4,2,Background(pls-wait-connect-call)
exten => 4,3,DISA(no-password|from-internal)

I changed the password in and the extension. When I call in I enter my custom extension, enter my password and then get a dial tome. I would like to add a prompt to enter the number you would like to call ( I have the gsm recording already)

I can used the Read command to have asterisk listen for the number, but how can I make it so user enters the number they want to call followed by the pound sign and the asterisk connects the call. This way I can send user an error message if the number is not formatted right