Placing string at the end of the strings.

Hello Everyone,

At the end of my program loop, I concatenates two strings
and insert into a main string. The results of the next set of the strings
should come after the previous strings.

1. e.g. mainstring = str1, str2.

The new concatenated string out of the next round of loop
should go and place it after str2. in the same mainstring.

Any suggestion on how to achieve this?

Thanks a lot in advance.

Thanks and Regards, Pradeep