Constrain objects when editing

If a I have a large cube and in it is a smaller cube and I resize the smaller cube I don’t want the smaller cube to clip and become large then the large cube. I was trying constraints but I can’t seem to get this to work.

Also when using the scale tool, is there away so when it is axis locked it resizes in only one direction and not both along the axis without having to go into edit mode and select the face and move it?

Also when using the scale tool, is there away so when it is axis locked it resizes in only one direction and not both along the axis without having to go into edit mode and select the face and move it?
Position the 3d curser on the face you want locked and then set the pivot point to the 3d curser (select pivot point on 3d view header or period key)

Thank you, that works well enough.

And I managed to figure out my first question, I put a boolean modifier on the smaller object and set it to intersect mode.