I'm trying to have a simple auto filled entry on the 1st page of my document

Pages 1 through X
Figures 1 through Y

X is easy - Field 'NumPages'
Y is not.

Is there a way to get the number of figures to be determined? If it helps all figures have a caption. All my googlefu has not helped me, i've tried looking as options for a long time with no luck. I'm not sure the best approach for this.
Any help or suggestions would be greatly appreciated.

Thanks