This seems to work:
datevar start := {?start};
datevar end := {?end};
numbervar sats;
numbervar suns;
sats := datepart("ww",end,crSaturday)-datepart("ww",start,crSaturday);
suns := datepart("ww",end,crSunday)-datepart("ww",start,crSunday);
if dayofweek(start,CrSaturday) = 1 then
sats := sats +1 ;
if dayofweek(start, crSunday) = 1 then
suns := suns + 1;
"Sats: "+totext(sats,0,"") + " Suns: "+totext(suns,0,"")
-LB