Need help with photoshop actions

I am trying to record a photoshop action that saves for web, and sets the height to a certain value, and the width will scale accordingly. The problem is that when I click record action>save for web>and change the height, photoshop sees that as changing the size of the image (85%). Since all my photos are different sizes I, of course, dont want it to change the size of all the photos to 85%… I hope you understand what I mean. Is there any way to make the action chnage the height of each photo to a certain size, and then adjust the width? I have too many photos to do this manually.