dragdrop misunderstanding

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hello
First of all, I think I should explain what I want to do so you can tell me if this is possible.

|label1|label2|label3|label4| etc...=the labels-problems
|label5|label6|label7|label8| etc...=the labels-solution

This is a software program that generates random numbers, but respecting aconstraint of size. These numbers appear on the labels 1 to 4. By "drag and drop" students should place the contents of these labels in ascending order (or low) in labels 5 to 8.
To provide a visual aid to students, I would like the label (1 to 4) change in appearance if it is already used in one of the labels (5 to 8).
Labels 1 to 4 have the the property AllowDrop = false.
Labels 5 to 8 have the AllowDrop property = true.
If the content of the drop comes from the labels-solution, then the content of the label-source must be clear: this looks like a move. If the content of the drop comes from the labels-problems, then the content of the label-source must be copied.
So the label 5 can receive some content from label 8, for example. That complicates the way to bring a visual aid ...
Moreover, I tried to create a user control inherited from a label that would be able to handle everything that is described above.
It is therefore much to learn at the same time, for an "old néophite" like me .
I managed to do most of what I described with VB 2008 Express, except for the ability of software to provide a visual aid.
I hope these explanations illuminate my first request.
pascal

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