stripping out all characters from a string, leaving numbers

[kowdyersazt#rancom[a..z]42]

Hay, i have a string like this:\[code\]v8gn5.8gnr4nggb58gng.g95h58g.n48fn49t.t8t8t57\[/code\]I want to strip out all the characters leaving just numbers (and .s)Any ideas how to do this? Is there a function prebuilt?thanks