If then else statement help

I am trying to write a formula to display the pledge Balance if it is null then the Payment amount if it is null then the Scheduled installment if there is none then the outright gift

//ie Ted paid $32,507.  This was applied to a $50,000 installment and the remainder to the next installment of $12,500 this means CR shows:

// the first balance as $0 with a $32,507 payment

// the next installment shows a balance of $11,994

//the next installment is $12,500

//so I want the formula to display:

//$32,507 then the next line $11,994 and the next line $12,500 

//what the formula below displays is:  $0 the next line $11994 and the next line is $12500

//this means the formula is not showing the payment


What am I doing wrong?  Here is my formula:


if not isnull ({CnGf_1Ins_1.CnGf_1Ins_1_Balance}) //installment balance to catch partial payments

    then {CnGf_1Ins_1.CnGf_1Ins_1_Balance}


else If not isnull ({CnGf_1Ins_1Py_1Gf.CnGf_1Ins_1Py_1Gf_Amount}) // pledge payment

then {CnGf_1Ins_1Py_1Gf.CnGf_1Ins_1Py_1Gf_Amount}

   

else if not isnull ({CnGf_1Ins_1.CnGf_1Ins_1_Amount}) //scheduled installment

then {CnGf_1Ins_1.CnGf_1Ins_1_Amount}


else {CnGf_1.CnGf_1_Amount}  //outright gift