I asssume you wanted to know last row added in grid is duplicate or not of above added grid rows?
if so, On click of submit button, call Activity. In the activity get the last row of grid from the list by using the PageList(<LAST>). returned page store in single page say "LastRowPage". now LastRowPage has the properies of Level1,Role,Access.
Now in the activity use for loop using page list. for each page list iterate and maintain a local variable duplicateFound.
for each loop iteration set the duplicateFound=false.
in the next step, check above three properies are equals to current list page. if three are equal then set duplicateFound=true. when duplicateFound=true, break the loop. also in parameter you can find forEach number. that number indicates which number is duplicate. and based on that number you can add message to grid.
if you are familar with data transform u can use datatrans too instead of activity.
Note: while iterating dont iterate till last row. last row is the one newly added which says always duplicate row. you have to iterate till the before last row. you can find when rule @pxIsLastInList(tools,.pageListProperty)