EXCEL GROUP ITEMS IN COLUMN B BY QUALIFYING DATA IN COLUMN A - HELP!!!

Experts,

Whether by macro or formula, I need the following:

I have a spreadsheet that currently has 2 columns.  Column A has numeric values sorted that can are not necessarily unique, thus you could see the below:

A
--
1
1
1
2
2
3
4
4
4
5
6
7
7
8
8
8

Column B has values that are unique, there are no duplicates and coorespond to the values in column A.  Thus column B could look like the below:

B
--
24
13
65
85
29
6
23
11
17
66
98
44
79
31
20
2

So together, we have this:

A              B
--             --
1      24
1      13
1      65
2      85
2      29
3      6
4      23
4      11
4      17
5      66
6      98
7      44
7      79
8      31
8      20
8      2

What I want instead of the above, is this:

1      24, 13, 65
2      85, 29
3      6
4      23, 11, 17
5      66
6      98
7      44, 79
8      31, 20, 2

I don't anticipate having more than 10000 rows (ever) and right now have under 1000.  Thank you very much...!!!