What is the 'value' of a grey check box? 1

[jeffmoore]

I have a form that when it is open the checkboxes appear in one of the three states; checked, not checked, or greyedout. The checkboxes are NOT triple stated. I need to be able to test (in vba) for the grayed out boxes. when i tried to look at the oldvalue for one of the greyed boxes it returns a zero.
Tia
Jeff

 

[jrbarnett]

Hi,

It should be Null.

John

 

[jeffmoore]

Thanks
I found out that for the checkbox to return NULL the box needs to be triple stated.
The above according to the vba help.
Well... when I triple stated the checkbox and then test for mycheckbox.oldvalue I still get 0.
I tried setting the default value to null, doesnt work.
i still get 0
There is next to no help in the vba help file on checkboxes.
So I'm still lookin...
TIA Jeff

 

[jeffmoore]

Okay more info on the problem.
using a before update event I halt the code at the opening line and look at the properties for my checkbox.
BOTH the old value AND the present value are changed.
ie: the box was grey --> I click on it it is checked.
prior to the before update event both properties are null.
then BOTH are -1 during the before update event.
Any suggestions?
Jeff

 

[KenReay]

Hi

Have you tried the obvious

If IsNull(chkMyCheckBox) Then
..etc
end if

???

Regards

Ken Reay
Freelance Solutions Developer
Boldon Information Systems Ltd
Website needs upgrading, but for now -

http://www.kenneth.reay.btinternet.co.uk

UK

 

[Eupher]

Just curious, why do you wish to test for the grayed out state? If your checkboxes are unbound and you haven't specified a default value, grayed out is how they will display when the form is opened, even if they're not triple-state. Post a little more info about what you are trying to accomplish and maybe we can advise you better.

Ken S.

 

[jeffmoore]

First yes i have tried the obvious.
I have a form that is based on three tables with ref. integrety set.
when the form is diplayed (as a continuous form) there will be valid values for some of the checkboxes. these are the only checkboxes i want the user to be able to manipulate. If the check box is grayed out then there is no valid record in one of my associated tables and I get the error message form access stating that i cant add a record as there is no associated record in the primary table.
well if i get that error i have to close the form and reopen it to clear the error. I'd just like to trap any click on a checkbox with a null value.
I have look at the variables using the vba watch, and locals windows and the state of the checkbox is not what i beleive should be the predictable behavior.
I hope this explaination help.
Try building a form with one checkbox on it and put code in the OnEnter and OnBeforeUpdate events. Place a break in both events at the first line possible and set up a watch on chkbox.value and chkbox.oldvalue at both events
on the onenter:
both values are NULL
onthe the onbeforeupdate:
oldvalue = 0
value = -1
try it and help me understand
Thanks alot for your time
Jeff

 

[jrbarnett]

Hi Jeffmoore,

If your tick box is there to indicate the presence of a record in a related table, then your database is not normalised, because the data includes redundant information.

Instead, why not put code in the BeforeUpdate event of the primary key do do a DLookup of a record in the related table - if it returns null then you can display a friendly error message and set Cancel to true; much nicer than Access built in error messages.

John

 

[Eupher]

Hey, Jeff,

Why not give something like this a try in the checkbox's Mouse Down event...

If Me!chkMyCheckbox = True Or Me!chkMyCheckbox = False Then
    'process normally
    Else
        MsgBox "Nyah, nyah, you can't click me!"
        DoCmd.CancelEvent
End If

HTH...

Ken S.

 

[jeffmoore]

THANK YOU EUPHER!!!
Nice and simple, I'm not sure I understand the root of the problem, but at this point I dont care!
Thanks to everyone for their input.
And if anyone figures out why the null test won't work or that bit about the events I worte about, Please post it
THanks again
jeff

 

[tormented]

I have recently seen in a book that the value of check boxes can be 0,1, and 2. One for unchecked,checked, and greyed. I can not remember exactly what value for each. I will try to get the exact name of the book and page number to help. I will try to post everything by tomorrow .

Tormented

 

[jeffmoore]

According to the help file in access, the values for a checkbox are: -1,0,null which result in the visualization of checked, not checked, and gray.
Jeff