Combobox sorting

I am writing a program that retrieves the names of files from a selected folder then puts the names of those files into an array as well as a combobox. The files are named identical with the the exception that they are numbered IE

XXXd1-1
XXXd1-2
XXXd1-3
XXXd1-4
etc
etc

There may also be

XXXd2-1
XXXd2-2
XXXd2-3
XXXd2-4
etc
etc

The test folder I have been using has twelve files so they are numbered 1 - 12 and are listed in order 1 - 12 in the folder. However in both the array and combobox they are listed as

XXXd2-1
XXXd2-10
XXXd2-11
XXXd2-12
XXXd2-2
XXXd2-3
XXXd2-4
tc
etc


How can I get the files listed as

XXXd1-1
XXXd1-2
XXXd1-3
XXXd1-4

.
.
.
.

XXXd2-10
XXXd2-11
XXXd2-12

I have sorted neither the array or the combobox.