I created a survey on Google Documents where people rate several items from 1-5. (I export the Google Docs results as an Excel file)

Unfortunately, Google Docs results include the text description in each cell, not just the numeric response: so the cells say "5 - Excellent" "3 - Satisfactory," etc. instead of just the numbers.

I know that I can get to just the numbers by
a.) Find & Replace to strip the text out OR
b.) Creating a duplicate table referring to each cell with "=VALUE(LEFT(F1,1))"

However, I will be updating this document regularly and I would prefer to sum directly from the original spreadsheet (downloaded as an Excel file) -- it would be tedious and error-prone to fiddle with option a or b.

Is there a way to sum the numbers directly from these cells?

I am able to add individual cells with a + operator like this: 
=SUM(VALUE(LEFT(F1,1))+VALUE(LEFT(F2,1)))
But trying to do the same with a range was unsuccessful: 

=SUM(VALUE(LEFT(F1,1)):VALUE(LEFT(F20,1)))
[resulted in error]

Is it possible to do this somehow?

Thanks