Code for checking that all fields on a SubForm has a record (based on a condition)

Question

I have a Main Form called Brewing.
On that main form there is a Sub Form (BrewingSubFormHops), see below.
"Min" is the time in boiling wort. Figure comes from recipe
"g/l" gram/liter, is the recommended amount of Hops based on wort in boiler. Figure comes from recipe
"added" is the real amount of hops the brewer should add into the wort.
"DryHop?" Yes / No. Data comes from recipe
If the "DryHop?" is No (0 ) then the hops will be added later, weeks later, and a record in the "added" field is not
required at this moment.
If the "DryHop?" is Yes (-1) then all the fields "added" must be completed before closing the MainForm/SubForm.
Picture 1 shows the SubForm that is right.
Picture 2 shows a SubForm with one missing data in field "added". How can I avoid this by prompting the user to "remember" to complete "added" on row two?
Best // Peter Forss Stockholm and Sigtuna GMT +1.00

Answer 1

Your form doesn't seem to agree with your description as in the former it is the rows with a Dryhop? value of TRUE which are NULL in both examples.  I'll assume the description is the correct basis.
In the subform's BeforeUpdate event procedure validate the data as follows, setting the return value of the Cancel argument to True if the validation criteria are not satisfied:
Const MESSAGE_TEXT = "Your message text goes here."
If Me.[DryHop?] Then
    If IsNull(Me.[Min]) Or _
       IsNull(Me.[g/l]) Or _
       IsNull(Me.[added]) Then
         MsgBox MESSAGE_TEXT, vbExclamation, "Incomplete Data"
         Cancel = True
    End If
End If
If it's the form which is correct rather than the description change the first line to:
If Not Me.[DryHop?] Then
You can, and in my opinion should, also enforce this in the table definition by using an appropriate expression as the table's ValidationRule property.
From a presentational point of view would it not be better to use a check box as the Dryhop column's display control, or at least format the column as Yes/No?  Access's implementation of Boolean TRUE and FALSE values as -1 and 0 is unlikely to be evident
to most users.
Ken Sheridan, Stafford, England