Repeating formula in other cells

[steve3730]

I have the below formula in my excel file and I have the formula repeating down. When I drag it down B21 changes to B22,B23,B24 etc and that is exactly what I want it to do, but D6 I want to stay the same the whole way. But when I drag it it changes to D7,D8,D9 etc. How can I repeat the formula have the B21 change but not the D6?

=IFERROR(VLOOKUP($B21,CHOOSE(D6,'100'!$A$2:$D$21471,'1400'!$A$2:$E$21471),3,0),"")

Thanks for the help
-Steve

 

[Tetra201]

Make it absolute:

=IFERROR(VLOOKUP($B21,CHOOSE($D$6,'100'!$A$2:$D$21471,'1400'!$A$2:$E$21471),3,0),"")

 

[JeanKim]

$D$6

 

[steve3730]

Thanks guys! Knew it was going to be something simple but was having trouble finding the answer on google

 

[Tetra201]

You are welcome.