string is number?

I have a string that is something like "http://bla.bla.com/etc/888777666/something/else" and I want to copy the number. The thing is that the number and its position varies.

My idea was to copy part of the string and use intcmp to see if it's a number, but I can't figure out how to do it.

Take a look at StrFilter in NSIS help file

thanks, I will use that, although it's not what I wanted.