New Formula Idea

I would like a formula that can equate a letter with an number, add the given
range, but also not do anything if there is a blank cell...

for example if i have a chart of a-e, and beside it a column with monetary
values. below this chart i have a calendarweek that has the letters listed
maybe a in day one, but maybe day two has both a and b, so the columns would
be day 1-7, and rows might be a-e... i need to sum the monetary values below
the calendarweek. i have tried using if then statments, and vlookup. the
problem is if there is a blank cell excel gives an error.

=IF(F10"",(SUM((VLOOKUP($F$10,$A$2:$C$6,3,FALSE) ),(VLOOKUP($F$11,$A$2:$C$6,3,FALSE)),(VLOOKUP($F$1 2,$A$2:$C$6,3,FALSE)),(VLOOKUP($F$13,$A$2:$C$6,3,F ALSE)),(VLOOKUP($F$14,$A$2:$C$6,3,FALSE)))),FALSE)

this is a formula i am trying to use, the problem is i start out with if f10
isn't blank then do my formula. if it is blank, type false. but if it is
false, then the rest are messed up b/c the formula uses all five rows and
without a value to vlookup there is an issue.

my suggestion is a formula that can reference a cell in this manner: the
cell might say A, but the value is 1000. so then you could just do:
=sum(F10:F14) and it would add 1000 + etc.

if you have further need for explaination, please let me know as i really
would like to figure this out without macros vba and the like.

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