I you really using a CrossTab or just a Report with Grouping that looks like a crosstab? Generally you do not have detail rows appearing a crosstab so I am guessing it is the just grouping.
If So you can use a Running Total or Variable. There aer tons of exampls on these but here is the gyst:
Create a Running Total as 'GroupedRowCount' (or whatever):
Field to summarize=anyfield that is not NULL on EVERY row (e.g. PrimayKey field)
Type of SUmmary= COunt (disctinctCount can often also be used on a PK field)
Evaluate=For Each Record
Reset = On Change of group (select the group required for your reset to 0)
Place on the detail row to see incrimental counting and on the Groyup Footer to see the total for that group (will be the same as the last row in the group)