Validation Rule

[Dado]

I almost read all posts about validation rules and I cant find solution for my problem.
I want to set that users must enter 13 numbers no more no less in form field,and if this condition is not satisfy I want to give warning to users with pop up massage.
Is it posible to make with validation rule or I must use code.

Please help me to resolve this problem.

 

[Moniker]

Set it up like this:

Validation Rule: Like "#############"
Validation Text: This field must be exactly 13 digits in length.

That forces 13 numbers only, and will display the Validation Text if the user puts in anything else.

 

[Dado]

Thanks a lot !!!