Access 2003

otpkma · January 28th, 2009, 02:23 PM

Have a table "tblData" and have a form frmDaily which in certain controls value is calculated with a Dlookup function from a tblREGMTOW when enter certain value in a control cmbRegistartion.

How can I lock (keep) the values calculated in the past in the form and do not alter even if we change the data in tblRegmtow.

i.e.
FORM
I enter a value in cmbRegistration which is stored in tblDATA, control MTOW picks the value with a Dlookup function from tblREGMTOW.

several dates later MTOW in tblREGMTOW has to change

Here comes the problem all form viewed MTOW's are changed to the new value even in the past, (How can I do That without adding a field MTOW int tblData to store the past values.

Thx
AA

mmcdonal · January 29th, 2009, 04:13 PM

You didn't post the code, but you could enclose it in:

If IsNull(Me.MyControl) Or Me.MyControl = "" (or Me.MyControl = 0 if it is a number) Then

'do dLookUp function

End If

You can put this on the On Current event, and the Before Update event, or where ever the code appears. Can you post it if you need more help?

otpkma · January 29th, 2009, 04:25 PM

Quote:

Originally Posted by mmcdonal

You didn't post the code, but you could enclose it in:

If IsNull(Me.MyControl) Or Me.MyControl = "" (or Me.MyControl = 0 if it is a number) Then

'do dLookUp function

End If

You can put this on the On Current event, and the Before Update event, or where ever the code appears. Can you post it if you need more help?

below code is in the MTOW control source which appears only in the form in the form

=DLookUp("MTOW","tblREGMTOW","REGISTRATION = '" & [REGISTRATION] & "'")

Thank you for your help it looks like that have to create a code for that.

brgds
Apostolis

mmcdonal · January 29th, 2009, 04:31 PM

So this is not a bound control? If it is bound, do this on the Before Insert and the Before Update events:

Code:

 
If IsNull(Me.MTOW) Or Me.MTOW = "" Then
 
   Me.MTOW=DLookUp("MTOW","tblREGMTOW","REGISTRATION = '" & [REGISTRATION] & "'")
 
End If

Then Lock the control to make it uneditable by the user.

This way the value will be calculated when the record is created, and recalculated if the record is changed AND the control is empty for some reason (for old records, mostly.)

Did that help?

otpkma · January 29th, 2009, 05:19 PM

Code:

If IsNull(Me.DLookUpMTOW) Or Me.DLookUpMTOW = 0 Then Me.DLookUpMTOW=DLookUp("MTOW","tblREGMTOW","REGISTRATION = '" & [REGISTRATION] & "'") End If

Used above in "Before Update" event, as the control is not bound to any table field, it looks that, keeps seeking the value from the DLookUp function in the "Control Source." removed the function from Control Source and than becomes blanc and Unbound, which is expected.
By the way the correct name of the control in the form is "DLookUpMTOW". and the format is Standard Number (FYI the value is the MaxTakeOffWeight of an Aircraft)

Thanks any way need reading and learning as not very experienced in Access, besides that have created this small db on my own to help and manage their day-to-day work in the office.

Thx once again for your help,
Apostolis