The following function returns the mean average of all the parameters passed to it, skipping any with a null value:

function mean( )

local nRet, nArg, nCnt 

nTot = 0 

nCnt = 0 

for nArg = 1 to argcount( ) 

if argvector( nArg ) # null 

nTot += argvector( nArg ) 

nCnt++ 

endif 

endfor 

return nTot / nCnt