Question: How can I Reverse a Fibonacci number and find the numbers between a range 20 and 20000 tia sal2

How can I Reverse a Fibonacci number and find the numbers between a range 20 and 20000 tia sal2

Greetings All

I've been able to figure out how to get the next fibonacci number in a
sequence given just one number using the floor command see below

x := 987.23
floor((x+sqrt(5*x^2))*(1/2))

What I'm trying to figure out is:
1) floor doesn't take into account decimals and I would like to
2) I would like to be able to find the fibonacci numbers in reverse
between the range of 20 to 20,000

Example:
If I put in 7778742049.8764 which is around fib(49)  I would like for it to come back
with all the fib numbers between 20 and 20,000 like Fib(8) which could be 21.234 fib(9) which could be 39.2345 etc...  Is this possible  (Note: the 21.234 and 39.2345 numbers are just
example numbers)


tia sal2
ps I'm using maple 12