Wanting Format Value to return altered version of %bpm% in "%bpm%-%initialkey%

As title explains, I am wanting to use Format Value action to bring BPM (%bpm%) and Key (%initialkey%) together in the Grouping (%contentgroup%) field.

However, bpm comes up as e.g. "00103 BPM" and I am only wanting to return the "103"; or if it was "00097 BPM" I want "97".

So I am wanting to do this:

Grouping- (nothing or something)
BPM- 00103 BPM
Key- 5A

Grouping- 103-5A

Thanks in advance

I would proceed as follows:
Format value for field %contentgroup%
Format string: %bpm% %initialkey%

Replace action for field %contentgroup%
Search: BPM
Replace with: -
(juggle a little bit the the blanks around BPM to get the result just right)

Replace action with regular expression:
search string: ^0
replace string:
(nothing, leave empty)

You can use the Mp3tag converter "Tag - Tag" or the action "Format value".

Convert | Tag - Tag | ALT+5


Format string: