"I figured I could do this via an Excel spreadsheet but can't see how that could be achieved."
If I'm understanding you correctly, in Excel (2003), I would have the first column (A) for entering the title of the song then in the 2nd column (B) enter the Disc number, ie 1, 2, 3 etc
Once you have entered all your songs and which disc, then select the two columns that now have content, click on Data (along the top), Sort and choose to sort by column A.
Note, you must have both A and B columns selected to do this, otherwise the rows of A and B will get muddled up.
I use Excel 2003 but the same principle should still stand in Excel 2007 I would have thought.
I hope this has helped you?