The relation attribute @ONNOVALUE is  attribute 

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Syntax

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Place 

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Arguments

• ParameterName defines the parameter containing the error message. You can also directly type the message between quotes. 
• MessageCaption is the caption of the message box presenting the error. 
• Action is optional, when no action is given, Quaestor will stop. When continue is written, Quaestor will continue after the message.

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