For invoices, quotes, work orders, or other forms, it IS possible to define a Related Row data type in the header area of the spreadsheet, for choosing a Contact Name from a separate customer list database contained in the same workspace. Done - works great.
Next step: Is there also a way to use VLOOKUP or some other function to do a lookup based on the Customer ID to return the address information? If so, what is the syntax for referencing a range in a different worksheet? Something like this?
Note that this is not the same as a Related Row Lookup because it is not within the Table area. This information is in the Header area.
One idea would be to create a new function for use in formulas that would work like this: =RRLOOKUP(related_row,field_name)
where related_row is a cell reference to a Related Row data type (the Customer ID in this case) and field_name is either the column number or name you want to return.