First let me just say this is all new to me, but I need to know it as it will make my job much easier, so I am willing to learn.

I need to merge 2 excel files -- I did do a search but due to my rookie-ness, I wasn't even sure what I was reading -- They both contain similar info. Product, description among others. One (sheet A) is updated about every 15 minutes and the other maybe once a month. So, sheet A is the best one for me to use for my job.

Sheet A has Product #, inventory, product cost, weight and a summarized description.
Sheet B has Product #, detailed short and long descriptions, MSRP, category, weights, and a bunch more related.

I need to get the cost information from sheet A (cause it's most recent) to match with sheet B by product number. If a product gets discontinued, it is removed from sheet A, whereas sheet B will contain until the next major update. This is why the product # field must match with desc. etc. I use the sheet A to upload all products to our website. Once I have all the columns matched up (which takes forever) I just format the sheet to specs and I upload it. I have tried copy this paste that in the past and have run into some trouble making sure descriptions are lined up for the relevant product #. I have run into prices not matching prod. #'s, as well as descriptions or categories being wrong.

I was hoping there was an easier than "copy & paste" way to do this. Please help if you can and I appreciate any help in a "walkthrough" manner that you can provide.