Even in SQL Server grouping islands of data is not too simple of a problem.
I suggest you to read this blog post - I believe the original solutions can be applied to VFP:
Refactoring Ranges


>Dear Experts
>
>Table1 has following Data
>
>
>S_NO -- CODE
>1------ 1102
>1------ 1102
>1------ 1103
>1------ 1104
>1------ 1201
>1------ 1202
>1------ 1203
>
>
>I want to replace s_no as below
>
>S_NO-- CODE
>1------ 1101
>1------ 1102
>1------ 1103
>1------ 1104
>2------ 1201
>2------ 1202
>2------ 1203
>
>sno column must increment with 1 where code column changes