Concatenate field and string

Question

I'm trying to concatenate a field with as string on FastReport and it's giving me all sorts of error.

My last attempts were:

[IIF(<fmRelOFtbTemp2."GROUP"> = '02', <fmRelOFtbTemp2."Weight"> & 'kg', '')]
[IIF(<fmRelOFtbTemp2."GROUP"> = '02', <fmRelOFtbTemp2."Weight"> + 'kg', '')]
[IIF(<fmRelOFtbTemp2."GROUP"> = '02', <fmRelOFtbTemp2."Weight"> & "kg", '')]
[IIF(<fmRelOFtbTemp2."GROUP"> = '02', <fmRelOFtbTemp2."Weight"> + "kg", '')]

It only works if I use the field alone:

[IIF(<fmRelOFtbTemp2."GROUP"> = '02', <fmRelOFtbTemp2."Weight">, '')]