Use the three-formula running total technique.

First Formula: Initialize Formula:
whileprintingrecords;
global numbervar nMaleCount:=0;
global numbervar nFemaleCount:=0;

Second Formula: Calculation Formula:
whileprintingrecords;
global numbervar nMaleCount:= nMaleCount + (if {table.sexfield}='M' then 1 else 0);
global numbervar nFemaleCount:=nFemaleCount + (if {table.sexfield}='F' then 1 else 0);

Third Formula: Display Formula (Male):
whileprintingrecords;
'Male: ' & global numbervar nMaleCount

Fourth Formula: Display Formula (Female):
whileprintingrecords;
'Female: ' & global numbervar nFemaleCount

Place the Initialize Formula on a page header, the Calculate Formula on the detail line that has the {table.sex} field, and the Display Formulas in your page footer.