is it possible to give value of one datagridview to another and update it?(inside pls see my code)

hi

  i'd like to ask u a question

   basically i am doing function of undo.

  so first ido like this

  DataGridView tmp;

  tmp=this.DataGridView;

  then if i modified sth in datagridview

 i found the tmp is not the original one!! 

   i request ur help and any help would be appreciated

  thank u very  much in advance

best regards

martin