go to codejunkies and look up your game..pokemon diamond has a shedload so you may just want to pick out the ones you want
copy and paste the codes into a .txt file, but make the labels like this.. example (tip keep labels short because the text won't scroll)
@ label 1
12345678 12345678
12345678 12345678
@ label 2
12345678 12345678
12345678 12345678
12345678 12345678
12345678 12345678
@label 3
12345678 12345678
save it, and then run it through AR2CHT.exe (available at the supercard site, just check the software for your type card)
this will produce your .cht file
then run that through cht2supercardcheat.exe (also at supercard site)
this will produce your .scc file (note, don't put the .txt file through, it needs to be the .cht file)
so example pokemonD.txt->pokemonD.cht->pokemonD.scc
then just patch the rom and goto properties and tick 'enable cheat' and direct the browse box to your .scc file
edit.. heres a quick one i made, you'll have to work out my labeling though
http://www.yourfilelink.com/get.php?fid=345260