Hi

P.e. you have manufacturer numbers on Sheet1 in range Sheet1!A2:A1000, and on Sheet2 in range Sheet2!C2:C99.

You enter p.e. into cell Sheet1!X2 the formula
=ISERROR(VLOOKUP($A2,Sheet2!$C$2:$C$99,1,0))
and then you copy it to range Sheet1!X2:X1000. Manufacturer numbers in rows where the formula returns FALSE are missing from Sheet2.

In similar way, you enter p.e. into cell Sheet2!X2 the formula
=ISERROR(VLOOKUP($C2,Sheet1!$A$2:$A$1000,1,0))
and then you copy it to range Sheet2!X2:X99. Manufacturer numbers in rows where the formula returns FALSE are missing from Sheet1.