Finding converted number from different worksheet

Hey there...
I have a batch of numbers that need to be converted to their corresponding number... I have a workbook, lets call it 'CoastConversion' that has two columns of numbers... Column A is WestCoast and Column B is the EastCoast equivalent of the number... what I need is a code that will do the following:
-Take the list of numbers (usually in a blank worksheet 'Sheet1' in Column A)
-Find it in column A (WestCoast) in the 'CoastConversion' workbook and copy its converted value from column B (EastCoast)
-paste its converted value to Column B on 'Sheet1'

I hope this makes sense... I just want to find an easier way to convert these numbers than copying each individual cell and then using the Find function to locate it in the conversion workbook ('CoastConversion')
Please let me know if I am not being clear enough or if i can provide any additional information... And as always... THANK YOU for any info you can provide! You guys are life savers on this website