Looking to limit characters to the field size with no scrolling

[spiced]

I'm using Acrobat 7 Pro. and created a form using Adobe Designer 7. I have a text field that has space for about 312 characters of 10 Arial (or 4 lines of text) if only text is used, no paragraph/carriage returns, then the spacing is fine. If returns are used it will push the text past the bottom border of the field and a scroll bar appears at the side of the field. Most of the people who will use the form will fill and print with Acrobat reader and anything they type below the bottom of the field won't print. How can I prevent the text from going below the bottom of the field?