How to append previous data InputFormTextBox on custom form

Hi All

I am using custom aspx form and using InputFormTextBox  on my form . I  am pulling data from multiple line of text field where append data to exisitng text is enabled .

How to bind this , which property /changes are required to achieve this as in sharepoint form it displays.

Please any help will be appriciated ..!

TIA

Thanks,

M

Manesh G