Paragraph type problem

I am creating a poster with text boxes that must all be the same font size for consistency.

I enter paragraph type and can resize the box without changing the font size. However when I go back to it later to resize/adjust it again it scales the text size as the bounding box changes.

How can I stop this because I will end up with a mess of different font sizes?

I have read the manual but gives no help once the text has been "committed" by removing the focus to another box.

THanks John I

Thanks for the input. It seems that if the text is created as "paragraph" type and then by clicking with the text tool in the text a box appears that can be adjusted without font size changes.

However if the text was created in "point" type this does not work. So - can I convert point type to paragraph? In future I will remember to create in paragraph mode if I need to change the layout box shape without font size changes.

Thanks for your help so far.