>I need to replace all standard textboxes on forms in a project to a textbox class I have created.
>
>I wrote a program that went through each form in the project, used it as a table and replaced the class & classloc fields with the correct class and class library name.
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>All went fine and the app runs properly.
>
>Whenever I open and then close a form in design that has the textbox class on it however, I am unable to then open the textbox class - a dialog box states = "Unable to modify a class that is in use".
>
>It is as if the class is opened when the form is opened but is left open after the form is closed.
>
>Any ideas as to what is going on ?

You may try to compile each classlib explicitly, before doing any editing or building. VFP may be detecting a conflict between the content of class/classloc and the compiled properties, and thus giving this message.