Sending email based on cell content

Ok, i'm going to try and explain this the best I can. I am very new to Excel programming but i do have a Visual Basic programming background so I should be good to go :-) Anyway, I've got a worksheet that has various order information in it. There are numerous calculations done to determine things. If these criteria are not met, a cell is populated with the word REJECTED in it. Now there are 16 possible fields that can have this REJECTED in them. What i want to do is have those cells monitored and if REJECTED is placed into that cell, to generate an email letting the customer know why the particular order was rejected. I have the email macro figured out already but am having problems with the monitoring of those cells. Any help would be greatly appreciated.

Thanks!

Justin

Thanks for the quick replies guys! That helps out a lot. Now, what if instead of clicking on a cell or such, if the criteria was met to make the REJECTED populate the cell, a commandbutton would show up, then you could click that to generate the email...is that something that is possible? Maybe have it hidden and when the cell is populated, it shows up..otherwise, not visble....