If/else if/else syntax question

I am trying to write a (java) script where the value of the field would be determined by the value of another field.  For instance, if field1 is less than or equal to 50000, then 0 would be in field2,...else if field 1 is greater than or equal to 100000, then 0 would be in field 2....else field2 would be a calculated field (Field1*20/1000).

The actual script I used is:

if (RenoCost <= 50000)

{NumericField3 =="0"

}

else if (RenoCost >= 100000)

{NumericField3 == "0"

}

else

{

NumericField3 == "RenoCost*23/1000

}

Thanks

Bonny