Forms :: New Record Default Value Not Working

I have a form where the control source of several text box fields includes a function that looks up values in a table that is not the form's record source. The default value in the property for these fields is set to 0. Unfortunately, when I migrate to a new record, these fields display the dreaded #Error. It should be noted that these fields are for display only and are not even in the form's underlying table.Here is an example of the control source for one of the fields:

Code:

=GetFYSummary("Budget",[ProjectID],0,0,"PPE","frm_ProjectFinancials")

Here is the start of the code for the function:

Code:

Public Function GetFYSummary(strField As String, lngProjectID As Long, lngFYYear As Long, intPeriod As Integer, _
strWBSType As String, strSource As String) As Long

[code]...

I'm trying to cover my bases to ensure that the displayed value of the field shows 0 rather than #Error.I even tried including a breakpoint at the first line of code in the function and it is never even triggered when I move to a new record.As soon as I type the first letter/number in a field that is tied to the form's record source, all of these display values do change to 0 appropriately.