Validate Data using Class Module

I am struggling with creating a data validation button!

My spreadsheet has several columns (Invoice Number, Vendor, Amount Due, and Approval Date) in which a user fills out the userform and hits save and the data is entered into the next row of the correct column.

Now I would like to add a 'Validate' button to the spreadsheet which, when clicked, will run through each row and check that the values in each cell are valid entries (ie. Invoice number as string, vendor as string, amount due as double, due date as date).

I have created a class module, and some functions to create class objects from both the sheet data and the data from the userform (with help from others). I am in a little (read: a lot!) over my head with this whole class module thing, so if someone has some advice or better idea I would GREATLY appreciate it!


Excel Help Validate.xlsm

Thank you for your help! I will continue researching and working with this code. I really appreciate the jump start you've given me!