In default Max, there's a little button down in the bottom left of the Unwrap UVW window which toggles the coordinate entry between "Absolute" and "Relative".
Toggle this to Relative first (it's on Absolute by default), then select your UVs and type "1" into the little entry fields down in the bottom left, then hit Enter. The selected UVs should move by exactly 1 unit while retaining their shape.
If they don't retain their shape then you're probably still in "Absolute" mode and you'll just have set all their U or V coordinates to exactly 1.0, which will put them in a straight line. In which case, hit Undo
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Toggle this to Relative first (it's on Absolute by default), then select your UVs and type "1" into the little entry fields down in the bottom left, then hit Enter. The selected UVs should move by exactly 1 unit while retaining their shape.
If they don't retain their shape then you're probably still in "Absolute" mode and you'll just have set all their U or V coordinates to exactly 1.0, which will put them in a straight line. In which case, hit Undo
http://donott-lcad.blogspot.com/2010/02/accurately-offsetting-overlapping-uv.html