Excel 2007 : How to protect the size and font of text boxes, but allow new text?

Hi

I have been designing a standard template for users to input information, I want to be able to restrict the space these users can input information. I want to use text boxes as these are a bit more usable compared to writing text in cells

I have been trying to 'protect' these text boxes however when I do, I can't then add text to these text boxes. I really want to be able to fix both...

1. the size of text boxes
2. the font the text box uses

Can anyone help me out?

I have attached the file to this post

(For info, the text boxes are contained within the large, white spaced areas)

Grateful for your help!!