Checkbox to insert text without using macro or user form

[Linrox]

I have created a simple form in Word 2003 with various form fields.
When a checkbox is ticked, I would like it to insert some text at th
bottom of the form. Is this possible without using Macros or Use
Forms?

I can get this to work with a dropdown inserting text with the belo
syntax:
{If {dropdown1} = service "insert text"}

But I can't get the same to work with a checkbox:
{If {checkbox1} = true "insert text"}

Any help would be much appreciated