InfoPath Dev

Hi,

I have been working with infopath for a little while but do not have advanced knowledge of validation.  Hopefully someone can help me out here.

Part 1: I have a requirement where I need to concatenate 2 fields (both text, firstname and lastname)  I need to validate the sum of these two fields and verify that the sum is not greater than 20 characters.  If they are less than 20 characters, then the form can be submitted.  If they are 20 or more, then there should be an error to the user.  

Part 2:  It would be nice to also validate to restrict special characters and spaces in both of these fields.

Does anyone have any ideas on this?

1) Create a validation rule that goes something like if string-length(concat(firstName, " ", lastName)) > 20 then display error "Cannot be more than 20 characters"

2) Similarly you can also create a rule that checks for individual special characters, but this would be a little more hard coding.  Perhaps an easier way is just to check the existence of only letters both upper and lower case.