generate random numbers where the difference is always positive

I am trying to generate some numbers, such that the difference is always positive. the user inputs the number of digits and the amount of rows they want. for example 3 digits 3 rows will produce

971
888
121

I want to make sure the difference of those is always positive. is there some kind of algorithm I can use. right now i just have my program create numbers, then subtract them and if it comes out negative, it will do it again... and again. It is very slow.

I was thinking of first generating the difference and then adding to it until the amount of desired rows is reached. But i ran into problems if i generates a very large number.