counting cells in a column with specific data

I want it to count and fill in a range in column A until it sees a blank or notices the change in value in column B. In the example below i hope it shows what i need to do. i left the last group without numbers to show that is where it needs to start counting over again. i am basically wanting to count down 1st place 2nd place etc.... in divisions i designate for tournaments i manage. thanks for your time.

   A           B        C                 D
    1        mpo       john           doe
    2        mpo       jane            doe
    3        mpo       jim              doe

    1       mam       mickey          mouse
    2       mam       daffy            duck
    3       mam       elmer             fudd


            wam       smith            judy
            wam       wygul           beth
            wam       francis          monica

Manually, you could do this with a formula. In A1, put 1. In B1 and copied all the way down, put this:

=IF(B2="","",N(A1)+1)

Now, if row1 actually has column titles, you could just use that same formula from first row of data all the way down, don't need to enter the 1 to start it.

...and the same approach built into a macro:

Option Explicit

Sub AddCount()
Dim LR As Long
LR = Range("B" & Rows.Count).End(xlUp).Row

Range("A1") = 1       'Delete this line if row 1 is column titles

Range("A2:A" & LR).FormulaR1C1 = "=IF(RC2="""","""",N(R[-1]C)+1)"
Columns(1).Value = Columns(1).Value

End Sub

Your workbook doesn't match the sample chart you posted, you shifted everything over by one column and I imagine you didn't adjust anything in the formula

Put this in B7 and copy down:

=IF(C7="","",N(B6)+1)

Or use the adjusted macro (based on your sample sheet):

Sub AddCount()
Dim LR As Long
LR = Range("C" & Rows.Count).End(xlUp).Row

Range("B7:B" & LR).FormulaR1C1 = "=IF(RC3="""","""",N(R[-1]C)+1)"
Columns(2).Value = Columns(2).Value

End Sub

The more I use Excel, the more I realize I have so much to learn. It's a monster.