How to you pass variables in the BeforeUpdate and AfterUpdate of a form field?

[dk4300]

Hi!
Scenario:
'frmQuantity' has 2 fields: 'Quantity' and 'Change'. 'Quantity' is a number that is populated from a table. 'Change' is a % that starts out 0.00% and is only updated when 'Quantity' is changed.

How do I get the 'Change' field to show the % change of the 'Quantity' field?

I would like to get the 'Quantity' value by using BeforeUpdate, then AfterUpdate, then subtract the 2. I don't know how to make this happen.

I would appreciate any help.
thanks!!


.

[Rabbit]

Use a global variable to store the value.

[dk4300]

Use a global variable to store the value.

Could you please give me an example of how to do this?
Thank you!

[Rabbit]

You would just Dim the variable at the top where the option statements go. Then you can use it like any other variable. But it keeps its value through the life of the form.

[dk4300]

I really appreciate you looking at this! Your last post really helped because I didn't know that the variables would save to the form like that. I'm making progress, but for some reason my BeforeUpdate is pulling the AfterUpdate number (which means it always calculates the sum as 0). Do you see what's still wrong with this?
Thanks!!

Option Compare Database
Dim dblBeforeQTY As Double
Dim dblAfterQTY As Double
Dim dblChange As Double

Private Sub QTY_BeforeUpdate(Cancel As Integer)
dblBeforeQTY = Me!QTY
End Sub

Private Sub QTY_AfterUpdate()

dblAfterQTY = Me!QTY
FindChange

End Sub

Function FindChange()

dblChange = dblAfterQTY - dblBeforeQTY
Me.Change = dblChange

End Function

[Rabbit]

Here's what's happening, the BeforeUpdate event occurs after the value is changed but before it is saved. So because it occurs after the value has changed, it won't know what the value was before it changed.

What you have to do is, when the form loads, assign the current value to a global variable. And in the after update, calculate the change, and then store the new value to the global.

[NeoPa]

There is also a property of most data holding controls called .OldValue. This will enable you to find the difference more easily I hope.