I've written an Applescript that is almost working how I want it to. There are a couple more things that I can't seem to get quite right.
-- Paths to Excel file and output directory
set excelDirectory to "Macintosh HD:Users:scott:Downloads:Excel:"
set outputDirectory to "Macintosh HD:Users:scott:Downloads:Excel:converted"
tell application "Microsoft Excel"
activate
set theWorkbook to open workbook workbook file name excelDirectory & "excel.xls"
set maxCount to count of worksheets of theWorkbook
repeat with i from 1 to maxCount
set theWorkbook to open workbook workbook file name excelDirectory & "excel.xls"
set theWorksheet to worksheet i of theWorkbook
set worksheetName to name of theWorksheet
activate object worksheet worksheetName
save as theWorksheet filename (outputDirectory & ":" & worksheetName & ".csv") file format CSV file format
close active workbook
end repeat
end tell