Create a new date or appointment 'My Date' field.
Give the property "Display in Calendar" = true.
Fill this field on the "onChange" trigger of the 'Status' field like this:

–––
'My Date' := null;
'My Date' := if text('Status') = "open" then 'Date field' end 
–––

Birger

@Birger.. I am trying to do this .. Perhaps I am missing something..   First.. The "My Date" field has a property called "Show in Calendar" that can manually be set to Yes / No.   If I try to 'My Date'.'Show in Calendar' := true... I get a script error message "Expression does not return a record: 'My Date'.'Show in Calendar' .... 

So.. seeing "record" .. I then code..

let t:=this;

t.'Show in Calendar' := true;

I get a script error Field 'Show in Calendar' not found.. 

How can I script toggeling the ability to show the date on the calendar ?? 

I think what Birger was saying is that you use the Show In Calendar Yes/No field's after update trigger to set the value in another date field to null if the Show In Calendar is no and to the original Date field if it's set to yes.

You set the original (entered) date to have. property Display In Calendar = No and the new date field to have this set as yes.

In this way, the new date field will only have a value if the yes/no it set to yes and you only get a calendar entry where this is yes.

You could obviously have a more complex formula to calculate whether to display in the calendar but the essential part of this is to use the second date field which is only set a value when whatever criteia are met.

@Julian .. Yes... I have used that work around ... but was hoping I did not need the hidden field..   I guess I got lost in translation.. :)   Thanks Much.

I'm trying and trying to use Birger's formula but can't get it to work. Surely I'm missing something but I can't figure out where I'm wrong