vb.net max number in comma seperated string

I have a process that will build a string...

I need the ability to match a "set of numbers" against that
Pick out the highest number
And remove the lower numbers from the original string

Example
Original String  is "1,2,5,1002,1003,1004,1005"
Match Set  "1002,1003,1004"... in this 1004 is obviously the highest number

My revised original set is now "1,2,5,1004,1005"