Extracting numbers in a string

[AndyCamp]

I am trying to extract numbers within parenthesis in a string; the problem I'm having is that some strings may have more than one set of parenthesis; the numbers I want to extract will always be at the end of a string, just before the extension.

For example,

2017-08-20 MANAGEMENT REPORT (AUGUST) - MARK SOBEY (1111).PDF

I want to be able to extract the numbers 1111. I tried the following formula, but it's not working properly:

ExtractString({@Extension}, "(", ").PDF")

@Extension is a formula that combines the filename and the extension.

Any help would be appreciated.
AC

 

[IanWaterman]

try

Tonumber(Split(StrReverse(Split(strReverse({@Extension}),'(')[1]),')')[1])

Ian

 

[AndyCamp]

Thanks Ian. Worked perfectly.