Wa alaykumus salaam.
I can remember something close to that Du'ah but don't know if it reads alright, it goes as follows:
"Allaahumma Rabbee Yassir Walaa Tu'assir, Faja'alanee Amree Sahlan Yaseerah, Farham Bukaa'i Anta Jidlee Bi Afwika, Wa Fukka Aseerah."
Please can anyone HELP say something about its correctness and if possible translate it into English. Jazaakal Laahu Khayra!