trying to concieve for a girl at age 40..How?

hello just a short bio..about myself I'm 39 will be 40 in January and my husband is 9 years older we have 3 kids 2 boys 1 girl ,boys are 18 and 6 an daughter is 17 we always wanted to have 2 boys 2 girls we took a break for 6 years do to family finances and health and work .our health and wellness hasn't been better then it is now we feel great physically fit we work out eating healthy no physical or health problems.other then I was diagnosed with gallstones over a year ago..but they don't bother me at all anymore since I've cut alotta stuff out my diet and started exerciseing at gym 1-2 days a week.. we will be together coming up on 20 years..I have a preconception appt soon.just wonder how many woman in there 40s have had healthy successful pregnancy at 40 & who has tryed conceive a certain gender and was successful and getting the gender they was trying for and if so what did you do??..without ivf or a fertility doctor's help..cause that's not an option it's way to expensive.. thanks