Letter Only - Validation does not accept space

[MayaV369]

Hi
Letter Only Validation does not accept space, So i tried the Custom Fields moduleand customize the validation rules, but its not working.

I tried this in the Custom function by copying the textbox.

[A-Z\s]+
^[a-zA-Z]+(\s[a-zA-Z]+)?$
var RegExpression = /^[a-zA-Z\s]*$/;

Kindly point solution