Use format info in Excel Writer

The “Style for Cell” has the following explenation: “A cell (i.e. A1, B3 etc.) to copy the styling from for this column (usually some pre-styled cell in a template)”

If I use a template of formats in an excel sheet, how can I reference this format info to be used when writng my data into excel? For example: (Filename(Sheet1(A3)). What is the most complex form of generating this reference?