Yes, edit your field within CB > Field Management and under Parameters > Validation you can adjust the fields validation as needed. Text fields support REGEXP validation, which can be used to limit the characters to uppercase as needed. Example as follows.
Authorized input: Custom PERL regular expression
Perl Regular Expression: /^[A-Z_\W\d\s]*$/
This should match uppercase, numbers, and non-word characters. If you strictly want uppercase letters only then the below will work.
Perl Regular Expression: /^[A-Z]*$/
See your CB 2.0 Primer Book for further validation parameter usage information. For REGEXP information see the below site.
www.regular-expressions.info/