Compare worksheets and populate based on match
 

I have two worksheets that contain information about the same items
(JobNumber) with one sheet being more current than the other. I want to
update the old data with new data.
What is the best walk sheet.newdata and compare it to sheet.olddata and
update sheet.oldata with info from sheet.newdata?

On sheet.olddata I have several columns including:

JobNumber Hours Dollars Descr1 Descr2 .......

On sheet.newdata I have only columns:

JobNumber NewHours NewDollars

I want to walk sheet.newdata and for each JobNumber I want to see if it
exists on sheet.olddata. If it exists, I want to replace Hours and Dollars
with Newhours and NewDollars. If the JobNumber from sheet.newdata is not on
sheet.olddata, I want to add it to the next available row.

Thanks