Add up two or more texts and show them into 1 Textarea

[A.Qasim]

Greetings,

I am trying to add up texts from different scroll lists and show up in one textArea as a concatenated string as image shown below :-

I have tried converting the typed text to Unicode::UnicodeChar and then applying Unicode::strncpy but it completely replaces the text.

[A.Qasim]

the simple function I want to perform is that I get text selected from these 3 scroll lists and they add themselves and showup in the 3rd textArea. hope I make my question clear.!