How to use string functions in CBTA

I have a string "Credit MB warranty PT01210636 has been saved". How to fetch "only number" from this string in CBTA 7.2. What will be the split formula? My Try- I have stored the above string in "COMPLETE_TEXT" and I am using below split formula- %=Split($COMPLETE_TEXT$,”“)(3)%

But it is not working. Any help would be appreciated