Ive got yet another Photoshop question. Involving Panoramic

Hi all.

Hope you can help me here. Ive made HDR pano's for a while now. But i did it the wrong way, I made every pic an HDR THEN i made the pano . Then i realized its better to first make the 3 exposure pano's THEN make the HDR.

Now here is my question:
After i made the 3 exposure Panoramic's I want to make an HDR, But all 3 photos have to be the exact same width and height. HOW DO I DO THAT?? I know you go the adjust image size and type in the width and height manually but that doesn't work as they are linked and as you adjust the width the height changes at the same time.

Thanks in advance for your help
Andre