How to round an HMS number? [SOLVED]

[JMB]

I'd like to know if it is posible to round the seconds in a number written in HMS format.

Here is an example. I'd like to round the number 15º16'16.99968" to 15º16'17". The function ROUND produces the following results:

ROUND(15º16'16.99968", 0) -> 15º00'00"
ROUND(15º16'16.99968", 1) -> 15º18'00"
ROUND(15º16'16.99968", 2) -> 15º16'12"
ROUND(15º16'16.99968", 3) -> 15º16'15.6"
ROUND(15º16'16.99968", 4) -> 15º16'17.04"

It seams that ROUND first converts 15º16'16.99968" to its decimal equivalent 15.2713888, then rounds this value to the specified number of decimal places (for example for 3 decimal places -> 15.271) and then converts this value back to the HMS format (15º16'15.6")

So, does anyone know how to get 15º16'17"?