Delete Records

I have one table in my database (Microsoft SQL server 6.5). It has primary key with two fields one with ID and the second called Number.

Example:

      RID           Number
      123           1
      123           2
      123           3
      123           4
      123           5
      123           6
      321           1
      321           2
      321           3
      321           4

I want to update the above records in such a way that i need to have only the highest 3 number records and i want to delete rest of the records. That means in the above case for RID 123 i need to keep 4, 5, 6 and delete the 1, 2, 3 Once i delete the records i need to update the 4, 5, 6 to 1, 2, 3.

Is there an easy way to do this in SQL like using stored procedure? (Without writing small prgram in VB using record sets etc.)

Thanks