Help for c# project

hi all, i am working with a c# project windows application.it is a multiuser application.for this i need sum classses for validations of inputs ,sum important codes like managing login forms etc. the prob i m facing is at my mdi form i hav used tool bar on whose click a new instance of the associated form is created and it is displayed but if the button is clickd again the new instance is created again which i don want. i want to use the forms collection as i use to do in visual basic.that mean if no instance loaded of that form in memoery then only create the instance and load else show the loaded instance at top. how would i do this plz tell. thanks. govind [email protected]