Loop Query To Update Output Depending Upon Count Of Distinct Entries

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 wasn't able to get the solution.