How to block date field enter back date

It is not impossible but is complicated by the DatePicker.
The DatePicker has no events, in and of itself.
That leaves the Change event, which will fire every time a user keystrokes in the field.
Which is not a happy thing, to say the least.

AFTER the users leave the field, then the AfterUpdate event fires.
It's easy then to compare the value entered against today's date and either fire them back into the control, or blank the control, or msgbox them about the bad choice.

But blocking them from making a bad choice in the first place--that's very hard.

Thank you!!

The fun starts now.
The error messages if they don't enter a valid date aren't pretty and aren't controllable.
And if they make an error today and don't notice until next week, what then?

BeforeUpdate and Validation rules exist and work -- in theory, and in practice, on the developer's machine.
In userland, they quickly become an unhappy swamp of all the little things that make an app look unpolished.
Validating with AfterUpdate gives you better control than BeforeUpdate and Validation rules -- and puts YOU in control of what the logic does.
The other two options aren't going to let the user escape the field without putting in a date that is today or tomorrow.
Even when they don't know which date it should be, or should have left it blank.
Or accidentally changed a valid value from last week and now can't leave the original data alone.
And it'll drive them crazy eventually.

Validating ALL the data on the form before it gets closed or moved to a new record is usually the most amount of work, but the best way to go about things.  That's my hard-won experience, anyway.

Nick67

Hi Nick67,
Thanks for the message, the reason we put the message is because user(s) should finish yesterday's job and enter yesterday's date, but they finished today and entered yesterday's date to show that how many they finished on yesterday but which is incorrect, that's why we try to avoid this thing happen.

Hi Rey Obrero,
I have one more question regarding the answer that you provided, I do not know if I need to open a new ticket for that.  The code is doing what I need on the date field but the only problem I notice this morning was if user(s) enter the back date and they want to exit out the form (I have a Cancel button on the form for user(s), normally user users can click Cancel to undo everything), the message still showing unless they removed the date, is anyway that when user(s) click the Cancel button on the form, the message will not show.  I did try to put :
if me.text1< Date() then
    msgbox "Cannot enter back date!"
    cancel =true
   text1 = ""
   exit sub
 end if
but I got error message.

Thanks

I wrote this while you were posting your last result.
I do not know if I need to open a new ticket for that.
You may as well.

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You have an operational need.  Nothing wrong with that!
But both Validation and BeforeUpdate tend to have some unhappy side-consequences when you put them into production.  They both are very strict and trap a user in a control until their requirements are fulfilled, period.  And the error messages that can be generated (let's say a user enters text instead of date, by accident) don't look very friendly.

And things like
Between date() and date() + 1
Look nice -- but what happens over a weekend span?
Or a mid-week holiday?

There is much to think about, and get right.
An AfterUpdate event can be much more flexible that a Validation Rule.
And it's not as persnickety as a BeforeUpdate event, which can rub out the user's entry and leave them feeling trapped.
Even when you provide some mechanism for cancelling an entire entry, a BeforeUpdate can be squirelly

if me.text1< Date() then
     msgbox "Cannot enter back date!"
     cancel =true
    text1 = ""
    exit sub
  end if

This is not good code.
You would want Me.Text1.Undo and not text1 = ""
This is a date.  "" is not a date and is also not Nothing or Null--it is a value and a string value-- just a string value of zero characters

try

if me.text1< Date() then
     msgbox "Cannot enter back date!"
     cancel =true
    text1 = Null  'since this is bound to a  date field
    exit sub
  end if