Does anyone know how to procedurally verify that a file is available within a zipped file as well as check the date the file was zipped?

I am working on an Excel application with Visual Basic for Applications code that can sucessfully unzip a file I'll call "sales.txt" from the zipped file "salesdata.zip".

Within my VBA procedures, I need to verify that this monthly file, provided by another person on a shared drive and the zipped file is replaced each month, has a date that falls within the current month. I also need to know that sales.txt exists in the zipped file before I copy the zipped file to the harddisk and start unzipping it. I know how to work with dates in VBA, I just need to know how to get the date from a zipped file. The point of all this is to check whether or not the other person put the current month's zipped file on the shared drive, and if not, the program will be halted.

Thanks.
Jerry