Best way to find end of a number in string

Hi,

I'm wondering if Filter or regular expression or substring is possible, or if looping through char by char is the way.

What is sought is the position in the string of the first non-numeric character. Then I can extract the number only.

VAL is no good as it loses leading zeros and will skip a space.
I need to know e.g. if the number is "0001" or "001" And "0001 11" not be 111.

LOL sorry if crazy question but hard to explain!

Thanks, ABB