WTForms - validating a single field

[Rich]

Hey,

In addition to standard WTForms validation I'd like to validate each field individually (onBlur) using Ajax so that my client side and server side validation rules can be shared. I'm using a jQuery plugin for inline validation that supports Ajax - it demands the server returns a simple JavaScript array for example:

["firstname",false]

My form & handlers etc are setup and working, I'm struggling to figure out how to call the individual field's validate method - i just need to obtain the boolean result. Could someone point me in the right direction please?

Many thanks,

Rich