Make Number in formulae go up in increments

[gogeta1998]

Hello,

Ive written this formula, I just need to make it such that when you drag down the +1 goes to +2 then +3, +4 etc etc

=INDEX('UNID Reference'!L:L,IF(INDEX(B:B,MATCH(D5,A:A,0))="Generate New INST UNID",(COUNTA('UNID Reference'!B:B))+1,B3))

I've underlined and bolded the '+1'  I'm referring to.

Thanks

[#2]

@gogeta1998 

=INDEX('UNID Reference'!L:L,IF(INDEX(B:B,MATCH(D5,A:A,0))="Generate New INST UNID",(COUNTA('UNID Reference'!B:B))+ROW(A1),B3))

Maybe with +ROW(A1) instead of +1 and +2.