How to set up kinetic mode in Specord 210 plus

Dear Sir,

         I would like to determine urea in serum sample using urease-GLDH enzymatic UV method (Diasys test kit).How to set up the protocal for the test ?After we mixed the sample+reagent then OD1 should be measure then again in 50 second OD2 will be measured(2 point kinetic measure).I need the value of OD1-OD2( the difference ) then multiply by the fixed factor.This might be easy to measure using the protocal that already available in the Speccord 210 plus.I would like to know how to set up protocal for kinetic test.

              Thank you for your help.

                                   Sincerely,

                             Dr Med Vet.   Satis Pholpark