What kind of spaces are between your digits?
I'm with you. Without an example text it's only reading the magic ball.
@Peter Spier,
I'm with you, too.
(?<=\d) (?=\d{3}\>)
or
(?<=\d) (?=\d{3}\b)
or
(?<=\d) (?=\d{3}\D)
One of this greps is required to find the correct places. But like you showed in your last (own) example:
Product A56Z1 1 324.45
The space between Z1 and 1 324. will be also found. The question is: is this a right or a wrong position found???