Loop Query to update the output

I need to update the result depending upon the count of distinct entries.

Example

ID Employee Region State
1 ABC AMEA MI
2 DEF AMEA MI
3 XYZ APAC TX


I want the result as below

ID Employee Region State
1 ABC AMEA MI-1
2 DEF AMEA MI-2
3 XYZ APAC TX

since the count of Region is 2

I tried using DECLARE @intFlag INT and stuff but wasnt able to get the solution. ANy help would be highly appreciated.