If I understand you correctly you want the same piece of text to appear in 300 reports e.g. "Report compiled by John Smith" where you change John Smith for other names for future publication
I would do this by having a table to store the text. Then use dlookup to get the text from the table when needed.
So in your reports you have a Text Box. In the record source for the text box you can use the DLookup function so that the text appears in the report. You will have to do this once in all reports where you want the text to appear.
When you want to change the text, just change it in the table and then all the reports will reflect this.
hth
Chris