Photoshop :: Selecting Corner Handle In Distort?

under the Transform command I use the distort function quite a bit, usually to correct lense distortion. When using the distort function I use the mouse to select a top left or top right corner handle and drag it to a point where I am happy with the result. I want to do the same but instead of using the mouse I want to use the keyboard direction arrows to effect the same change. At present if I select the left top corner handle, and I use the keyboard arrows the whole image moves in that direction. It will not apply the same action as the mouse does. The reason for wanting to use the keyboard is I want more control over the correction. I find using the mouse a bit all over the place in getting the correct point.