I was about to go off looking for elegant VBA solutions or whatever, then I thought: 'Hang on. We just want to manipulate some data in a spreadsheet we own. Why complicate things?'
How does this idea sound to you:
insert a new column just after the column with the existing data (let's assume that is column C)
fill the new column with this formula: ="447" & RIGHT(C1, 9)
select column D (which now contains the new values) and Paste Values (which is in the Paste Special dialog) onto column C, replacing existing values
delete the 'working' column D
It's not programming but if you only have to do it once you don't need a program, right?
