Lookup Validation in #Nintex Form for #Office365

Business Requirement:

Description field should be valid for submission ONLY if the lookup control in the form  was a specific text.

Solution:

1. Add Rule to the associated control
2. Choose Rule Type > Validation
3. Select formula > Runtime Functions > parseLookup(Syntax: parseLookup([array or single lookup value], [optional bool showText]) ) remove everything in the hard bracket and select the desired control from your Named Controls reference section.
4. In the image below and for my requirement the working validation formula was: parseLookup(Reasonforchange)!=’Other’  as seen in the image below.
   

Now when a user tries to submit the form by typing contents the description control when the lookup control value is not equal to ‘Other’ they get alerted and will not be able to submit the form until the form values are fixed.