VLookup To Pivot Table Using Match Function - Returns Error If Can't Find Match Value

I am having some trouble getting a formula to work. I am building a report that pulls figures from a pivot table in another workbook. I am using a vlookup with match function to get the column index to find the relevant data I want. Where I need to add two columns together I am using sum, with the vlookup & match formulas nested in them e.g.:

=SUM(VLOOKUP(F13,'[PIVOT 156.xlsx]PIVOT'!$C:$AQ,MATCH("FAID",'[PIVOT 156.xlsx]PIVOT'!$C$6:$AQ$6,0),FALSE),VLOOKUP(F13,'[PIVOT 156.xlsx]PIVOT'!$C:$AQ,MATCH("COMM",'[PIVOT 156.xlsx]PIVOT'!$C$6:$AQ$6,0),FALSE),VLOOKUP(F13,'[PIVOT 156.xlsx]PIVOT'!$C:$AQ,MATCH("BPCM",'[PIVOT 156.xlsx]PIVOT'!$C$6:$AQ$6,0),FALSE),VLOOKUP(F13,'[PIVOT 156.xlsx]PIVOT'!$C:$AQ,MATCH("COMD",'[PIVOT 156.xlsx]PIVOT'!$C$6:$AQ$6,0),FALSE))

Where:
F13 = Employee number
Column C on the pivot 156 workbook is where the employee number is based.
The Match formula is then getting the column index from the column headings of the pivot table ie. "FAID"

This in itself works fine, as long as it finds a match in the column headings. This is where i get the error as in the above function "COMD" is not in the pivot table. However I need to keep it included as it may appear on a future pivot table. Is there a way of getting the sum function to complete even though later in the formula it can't complete the vlookup? So it will ignore it, or assume the value is zero if it can't find it? The formula probably needs to do this for all the vlookups as some headings may drop off in future pivot tables.