Hi Madhan KG,
I am not really clear about your question. I am giving try only by the inspiration from Hui's email.
I assume you are looking to add cloud to specific cell which is similar to comment box.
Firstly, to make comment box always appear irrespective of mouse move over the cell:
1. Insert comment
2. Right click Cell and toggle between show/hide comment.
Secondly, to make the comment box look like "Cloud", you need to select the comment box and convert default shape of box to Cloud.
This can be achieved with following steps:
in Excel 2003 Format:
1. Select the comment box
2. Draw > Convert Shape > Select Cloud (Or any shape of your choice).
In Excel 2007 Format: (you need to first get this convert shape option)
1. Goto Excel Options
2. click Customize tab
3. Under choose commands from drop down select > Drawing | Format Tab
4. From the list below select > "Change Shape" and Add
5. Click Ok.
Now you have the "change shape" option visible in excel window top left side (Quick Access Tool Bar).
1. Select the comment box
2. Click "Change Shape" in Quick Access Tool Bar
3. Select the shape of your choice "Cloud".
In Excel 2010 Format: (Should be same as Excel 2007, I do not have Excel 2010 so not sure.
I hope my understanding of your question is correct and addresses it.
Regards,
Prasad DN