Restrict IsPartOf function to one record

[MauriceWhelan]

Hi. I have a (Dresser Detail Master) table which IsPartOf a (Routings Master) table through [Record ID]. I want to restrict the user to one associated record only if possible so if the user submits a record on the (Dresser Detail Master) form and returns to the (Routings Master) form the ‘New’ option is not available. I have tried the following expression on the ‘Add’ action for the (Dresser Detail Master) table but the ‘New’ button is consistently invisible so that I can’t add even an initial record.

COUNT(
FILTER(“Dresser_Detail_Master”,
[Record ID]=[Record ID].[Routing ID]))<1

Is this the right approach and if so is my expression close to what is needed?

Any advice would be great, thank you.

[Steve]

Try setting the Only if this condition is true expression for the Add action for the Routings Master table to this:

ISBLANK([Related Dresser_Detail_Masters])

In the future, I encourage you to consistently use the actual names of the tables. If the name has underscores in place of spaces, please consistently use the underscores.

[MauriceWhelan]

Thank you @Steve for your advice