Regular Expression for one embedded space and forced upper cases?

[touseef4pk]

HI!
I want to write a regular expression which may enforce input in upper case and one embedded space e.g I want to give me input as "M23 9RQ". So please help me the regular expression for this input or some other better solution like customer validator etc.
Thanks

[Alsvha]

From what you mention - then off the top of my head, I'd say something along this line:

[A-Z]([A-Z ]+[A-Z])?