How can you change the height of a wall (strait or curved) starting from higher of the one end to lower to the other! like a trapezium! and what about id i want to decrease the height with curve??
If you place a roof at the correct angle along the top of the wall and trim to roof you can then delete the roof and the wall stays trimmed (unless you undo it in the main dialogue for that wall object).
With SEO the process is similar except that if the operator (or roof element) is deleted the trim is disappears, so to keep it you will need to group the operator with the wall and place it on a layer that is off in the model view.
Of course if the wall is curved and you want the slope along the length to be regular you will need to use a spiral ramp as the operator.