I have the following 3 formulas in rows 3-5

=INDEX(Master!$A$16:$C$43,MATCH(B9,Master!$A$16:$A $43,),MATCH("Subacc",Maste
r!$A$16:$C$16,))
=INDEX(Master!$A$16:$C$43,MATCH(B9,Master!$A$16:$A $43,),MATCH("Subacc",Maste
r!$A$16:$C$16,))
=INDEX(Master!$A$16:$C$43,MATCH(B9,Master!$A$16:$A $43,),MATCH("Subacc",Maste
r!$A$16:$C$16,))

I wish to copy them down to rows 6-8 so that the "B9" within them changes to
"B10". Currently if I just copy and Paste it changes to "B12". I'm sure its
a Offset formula I need but I can't figure it out. I have 400 rows in total
to copy down, so changing it manually would be a big effort

Thanks