ISNA in array formula problem

for data like this I prefer to keep it simple. If I need to concatenate 3 values for each row of data to get a unique "key", then I do so in a new column to make matching simple. I've added that key column with formulas to the data sheet.

Then in G4, this formula, copied down/across:

=IF(ISNUMBER(MATCH(IF($B4="", $B3, $B4)&$C4&G$3,'Market Samurai data'!$I:$I,0)), INDEX('Market Samurai data'!$E:$E, MATCH(IF($B4="", $B3, $B4)&$C4&G$3,'Market Samurai data'!$I:$I,0)), "")


Notice that some of your matches require you to "test" whether the B value is blank or not....