Replacing a material number in ztable

Hi Frds,

I have create a table control

Example : 1st. column , Material number & 2. Column is description 3.Alternative RM code 4 th is description.

Once i saved the above four fields in a ztable.Again my users going to use above fields in another transaction its replacing to new present document.

My requirement not to replace.........it has to remain in zdatabase table .

Please guide me