Hi Yugesh,
Here's what you need to do:
1) Create a formula with this code and place it on the Details:
shared stringvar c;
if Instr(c, {Country}) = 0 then
c := c + {Country} + ', ';
'';
2) Create this formula to display the final string:
shared stringvar c;
Left(c, Len(c)-2);
-Abhilash