SQL & PL/SQL :: CLOB Column Append

I have a requirement when I need to append and show the contents of a CLOB (rich text) column into the Open office report.

The use case is as below.
User(s) can enter the details into a CLOB column.
This data entered by each user need to be concatenated onto another CLOB column which will hold all the history of changes. Mainly i wanted to perform a concatenation of these two columns.

|
| User Entered | Stored |
| Data Stored in Clob Column 1| Data Stored in Clob Column 2 |
| v_clob_1 | v_clob_target |
-------------------------------------------------------------------------------
|"Text 1" and a image |"Text 1" and a image |
-------------------------------------------------------------------------------

Any method to achieve this case. I had tried the following method to achieve this. But no success.

v_merge clob;
v_clob_target clob;
v_clob_1 clob;

1)
DBMS_LOB.APPEND(v_merge, v_clob_target);
DBMS_LOB.APPEND(v_merge, v_clob_1);

2)
DBMS_LOB.APPEND(v_clob_target, v_clob_1);

3)
v_merge:= v_clob_target || ''|| v_clob_1;
v_clob_target := v_merge;