Is it possible to use the 'custom entry format' to force two words of any length in an input field?

Is it possible to use the 'custom entry format' to force two words of any length in an input field?

Hi, 
I have a zoho form capturing leads, one of the fields is a single line field for the validation I require a minimum of two words which can be any letter of the alphabet, the words are separated by a space.

I can't figure out how to write the 'custom entry format' to allow any length word, it seems to always restrict it to the amount of characters i enter for each word. Anyone got any advice?