Clear an error message created by a calculation

New to the whole forum thing and semi new to FM. Sorry if this gets long winded.

I am having a problem with overriding an error message that is generated by a calculation field.

I have a relational database for a magazine that I need input from one databse into the main database that I moinitor. I am working with time and date fields. The "Edit Log" (the main log) and the "Cover Log" (secondary log)

The Cover log is set up with a portal so that information can be input and viewed by the Edit log. Once a specific date and time have been entered into the Edit log, no new information can be entered into the Cover log. This all works great. I need to be able to clear the time and date field in the Edit log so that permission can be given to enter the new information into the Cover log. The problem is that just deleting the fields does not clear the rstriction.

I have set the fields as such:

Define Fields;

Type - Date

Options - Validated by Calculation {If(Cover OK = "",1,0)}

Strict: is checked and personal message attached.

Any help/suggestions will be greatly appreciated.

Thanks