It seems to me that you are suggesting synchronizing a function generator with an external standard. The answer is, it depends on the function generator.
If the generator is synthesized and uses a 10 MHz standard, say, you could in theory use the external standard and thus have what you want. If it uses something other than 10 MHz, you will have to generate that frequency from the GPS. If it doesn't work that way, you probably can't synchronize it because each frequency it generates is free running and has no standard.