Regular Expression

Question

I have to put validation for a text box .

Conditions :Must not be less than 12 characters and cannot contain punctuation, commas, full stops etc

I am using the regular expression validator and validation expression as [0-9A-Za-z]{12}.which is restricting punctuation, commas, full stops etc

I am not able to enter any value whose length is greater than 12.

We can do the validation by using  java script or by checking the length of the text box.

But I want know whether we can use validation expression which will allow to enter minimum 12 characters.

Please help me to resolve the issue.