Pre-set text entry

Hi Folks, I'm sure this is another stupid question but you never know until you ask ;-)

I have set up a simple way of using buttons to add pre-set text to a multi-line text field. With each button clicked; the text is added and a carriage return is applied. I don't wan't to overwrite the existing text in the field, just add to it. Currently all works well but I return an (unnamed) entry with the first button click on each new record. I understand why - I am using a let t := this + new text to ensure I keep the previous entries -  but is there a way around this? I have to be able to click any of the buttons first. Any help would be appreciated.

Many thanks