Word 2007: Can edit a default font using top styles selection boxes

[Des]

I have great difficulty in editing a style. When I select modify I have a text line at the botom that can be high lighted but not editable. I hae a drop down box to change a Font etc. but how do I change Line spacing: Multiple 1.15 to Line spacing: single. Should there not be a drop down box for ALL OF these settings are allow editing. There used to be a facility in Excelthat allowed you to edit a date format by editing the text 'DD/MM'YYYY'. There seems to be a lack of editability to thouse who know.