Loading images of different size

[size=3][font=Times New Roman]Dear all,[/font][/size]

[size=3][font=Times New Roman]I need your help to resolve this little problem.[/font][/size]
[size=3][font=Times New Roman]I am designing my web page in flash. I have a main movieclip (720x480) with three buttons. Each one loads a different movieclip. Once a movieclip is loaded the user can press more buttons to load images in a popup window (a simple gallery). This is where I can not go further. The size of images is unknown. How can I make a movieclip whose size changes according the size of the loaded image? I am using popup windows because the main movieclip is complete made of vectors and I want to show the images without distortion[/font][/size]

[size=3][font=Times New Roman]Your help will be well received[/font][/size]

[size=3][font=Times New Roman]Thanks[/font][/size]

Costa