Sorry i should have been more clearer.
I purchased WDC a few years ago at $10. This is the buy price which is showing on my commsec account. Now that my original holiding of WDC has been broken up into WDC and WRT and the value of WDC has been reduced, how do you work out what you have now paid for WDC and WRT? or do you just leave WDC as $10 and WRT as $0 payed. Hope this makes sense?