This is no easy task. You will have to capture your first mouse click, move your mouse and check the location of your mouse at the mouse release too. You can accomplish this with the
MouseDown[
^] and
MouseUp[
^] Events of your Form. Calculate the square you have drawn and give all the Controls in it some selected appearance (for example change the background color). Then comes the hard part. Moving them.
There are some pretty good articles about that, right here on CP.
Runtime Editable Control[
^]
Excerpt from the book World of Movable Objects[
^]
Move controls on a form at runtime[
^]