Problem with Custom Field Edit

To all,

I am currently on 3.6.4. In it, there are a few default validation 

settings for Custom Fields. One of them is:

(?#Digits)^[\d.]+$

When I use this, however, it gives an error even though i am 

entering numbers in the field. Has anyone else had this problem? What I
want it to do is ensure all entrees are numeric IF a value is entered.
Help anyone?

Kenn
LBNL