Alpha-Numeric Validations

Hi Gurus,

Can anybody help me out for alpha-numeric client-side Validation? I want to allow only numeric value. I did try using some Text Functions available and succeeded in not allowing 'Character Only' input but when the input has 'characters and digit' (alpha-numeric) the functions appear to be less helpful although i tried various AND OR conditions....

If anyone has tried this please let me know its a bit urgent.....