hello, I hope this problem I am having can be simply solved....

I need to sort all in one column the following sequence ( I use it for
managing keys that are made. Subsequent keys are enumerated by adding the
next sequential letter)
ex: 101, 102,102a,102b,103
Current any sort I use sorts it this way :101, 102, 103, 102a, 102b

What can I do to sort chronologically with the letters in the same column so
the result looks like this:
101, 102,102a,102b,103

If I add a key to 101, it needs to sort this way:
101,101a,102,102a,102b,103

can any one help, thank you