Combinations generator

I need a program/code, Matlab preferably, to generate a list of combinations from a list of numbers. For example, I'll have a list of 5 digit numbers (5,18,38,45,90) and i want combinations of 4, so the program will generate me a list like this, 5,18,38,45
5,18,38,90
5,18,45,90
5,38,45,90
18,38,45,90.

I need to have the option of changing how many different combinations i need depending on how long the numbers are. If the numbers are 10 digits long, i might want to have combinations of 5, which would be 252 total sets, etc. I also should be able to add a list of thousands of numbers at a time and the results to come out in a single excel column.