using Excel's regression analysis to compare correlation of FX rat
 

I'm trying to determine the correlation of foreign currency exchange rates
for the Thai Baht to US Dollar between Jan 1 and Dec 28 2007. There are two
rates, the on-shore rate and the off-shore rate. Using regression analysis,
what should I use as the X-Axis? How do I enter multiple rates for on-shore
and off-shore?