How to transfer a recieved mobile number for sending SMS to.

With Arduino Uno and SIM900 I can receive SMS (to do some remote controlling) and I can send SMS to a predetermined mobile number - no problem.
From time to time, I want to change the predetermined mobile number without new upload to Arduino.
I´m using the below well known code. I need to know how to code Arduino for translating the SMS with the new predetermined mobile number and code putting it into the below space for "mobile number"?

void SendTekst_1()
{  mySerial.print("AT+CMGF=1\r");    //Send SMS i text-mode
  delay(100);
  mySerial.println("AT + CMGS = \"[u]+45 predetermined mobile number[/u]\""); 
  delay(100);
  mySerial.println("Alarm i saddelrum 1!");
  delay(100);
  mySerial.println((char)26);//ASCII koden for ctrl+z er 26
  delay(100);
  mySerial.println();
}

Hi did you manage to solve this ?

No, I have so far not been successful doing this. Do you know?