...
var
i : Integer;
r : Double;
cp : TComponent;
begin
if TryStrToFloat(Edit1.Text, r) then
begin
for i:= 1 to 3 do
begin
cp := FindComponent('CheckBox'+IntToStr(i));
if Assigned(cp) and TCheckBox(cp).Checked then
r := r + StrToFloat(TCheckBox(cp).Caption)
end;
ShowMessage(FormatFloat('0.00', r))
end
end;