Time formulae to display current time based on (-5 -1 -10 (hours)) field

Could some kind genius point me towards getting the following result please?

Field one - Numeric integer - Values of +12 to -12 (inc 0)
Field two - Field to display current time +/- Field one.

i.e. Be able to view current time in field 2 of an record that has a GMT offset defined in field 1.

Thanks in advance.

…Jon.