Missing optional criteria causes error?

[tommycrock]

If I enter an expression with optional criteria as the Default value for a control, so the first criterion is missing and the second isn’t, I get the following error:

The expression you entered contains invalid syntax.
You may have entered a comma without a preceding identifier

This doesn’t happen in code.
e.g. using Allen Browne’s ELookup function (ELookup(Expr, Domain, [Criteria], [OrderClause])
I don’t want to enter criteria, so I enter:

=ELookup("[decisionID]", "qryDecisionStudy"[COLOR=Red][B], ,[/B][/COLOR] "decisionID")

This works in VBA code so why not from a property box? Or is there a way around this other than writing an alternative function that doesn't ask for the optional criteria and calls the one you want?

Thanks!