How do I make a button in an MS Access form create a date stamp, THEN not allow further edits?

Question

The code for the date stamp is simple enough.

Private Sub CmdMyButton_Click()
txtThingDateStamped.Locked = False
txtThingDateStamped = Now()
txtThingDateStamped.Locked = True
End Sub

But users can still hit the date stamp multiple times and it can be edited by other forms.

I used the MS Access Project Management template to start my adventure here. Specifically the two forms I'm working with are (1) "Project Details" and (2) "Project List".

Answer 1

You could use a Before Change data macro on the table to enforce the constraint at that level:

<?xml version="1.0" encoding="utf-16" standalone="no"?>
<DataMacros xmlns="http://schemas.microsoft.com/office/accessservices/2009/11/application">
  <DataMacro Event="BeforeChange">
    <Statements>
      <ConditionalBlock>
        <If>
          <Condition>Updated(&quot;ThingDateStamped&quot;)</Condition>
          <Statements>
            <ConditionalBlock>
              <If>
                <Condition>Not IsNull([Old].[ThingDateStamped])</Condition>
                <Statements>
                  <Action Name="RaiseError">
                    <Argument Name="Number">1</Argument>
                    <Argument Name="Description">An existing datestamp cannot be altered.</Argument>
                  </Action>
                </Statements>
              </If>
            </ConditionalBlock>
          </Statements>
        </If>
      </ConditionalBlock>
    </Statements>
  </DataMacro>
</DataMacros>