Hi Abhay - Your requirement is not clear.
If you want to concatenate multiple fields under a segment, you can use the concat function right??
if you want append multiple occurrences of a field, i.e. as item is repeating multiple times and you want to concatenate all the occurrences of field F4 then you can use below UDF.[i did not tested it.. may be you have to modify a little]
Input parameter will be F4 field and select the Queue in the Execution type..
String s;
for (int i = 0;i<=F4.length;i++)
{
s = s+F4[i];
}
result.addValue(s);
Regards,
Hareesh