Now see if your new data type works by creating a new visual part with one Text part and one Push Button part in a Window part. Open the settings of the Text part and select Even Number from the converter property's Data Type drop-down list. Change the label on the push button to Validate.

Test your visual part: try typing both even and odd numbers and selecting Validate after each number. You should see an error message (such as ** error **) in the field whenever you type an invalid value. If not, go back and check the acceptsAsDisplayToObjectInput: script you wrote.