Validation and Navigation

Hello:

I am making form application and I want to put validation on following;

1) Text box to accept characters only like A-Z and a-z and to show msg box if other then character entered.

2) Combo box to allow user to select option from list and if it try to enter anything msg box appear.

Also i want to put navigation on record like next record, previous record.

I am using Visual Studio 2012 express and language is VB.

Please reply as soon as possible.

Regard 

Abdullah Khursheed