Formula Advice on creating a group of sequence numbers to restart after 20 rows

[VBA learner ITG]

hi all,

I need your advice please as I am im sure its a simple fix but i cannot think of the solution.

The below formula creates a group of sequence numbers based on 2 colmns which works.

=IF(A1<>A2,1,IF(B1=B2,G1,G1+1))

However, I need it to restart the formula number sequencing after 20 rows of data.

Row 1 is the row headers.

from row 2 to row 21 would = 20 rows.

From row 22 to row 41 would = 20 rows.

Any help appreciated.

 

[Joe4]

OK, if it is really that straightforward, I think this addition would do it:
=IF(MOD(ROW(),20)=2,1,IF(A1<>A2,1,IF(B1=B2,G1,G1+1)))