The tool honours a selection.
Then you are asking about the xlwt package, not the 10.2 table to excel tool. You would have to define your selection in some manner. Generally by accessing the source table row by row using a cursor.
# Use row object to get and set field values
cur = arcpy.SearchCursor(layer)
# Set up workbook and sheet
book = Workbook()
sheet1 = book.add_sheet('Polygons')
# Set counter
rowx = 0
# Loop through rows in dbf file.
for row in cur:
rowx += 1
# Write each row to the sheet from the workbook. Set column index in sheet for each column in .dbf
del cur, row
Retrieving data ...