I am not sure what your lookup table is or where you would put your results,
but take a look at this.  I organized a price table as shown below

    Quantity    CostAmt
Lemons    20    
Oranges        $1,000.00
Bananas    30    
Grapes        $40.00
Cherries    2,000    

I used the insert name function to name the rows and columns with the fruit
names and quantities and CostAmt.

I used the following equation to check if a cell was blank and if so created
two possible outcomes.  In this particuar case, E9 contains the word
"lemons".  So if the above table at lemons quantity were blank, the equation
executes the first option in the if statement, and if not, it executes the
second.  You can substitute functions or lookups for the "zero" and "not
zero" entries shown.

=IF(ISBLANK(Quantity INDIRECT(E9)),"zero","not zero")

In this case I created a little table with thr first column with various
fruits (Lemons in E9) and copied it for the rest of the rows and got the
following.

Pricing   
Lemons    not zero
Oranges    zero
Bananas    not zero
Grapes    zero
Cherries    not zero

Hope this helps a little