Lookup Functions After Adding New Worksheet To Workbook

What I would like to do is have a master workbook that I can import different .csv files into as a new worksheet. Then calculations will be run on the values that are imported. My goal is to select a column and have corresponding list update the values. After that formulas will run on the calculations. I have got the import csv file down using VBA. The problem I was running into was with the Data Validation. Since I was overwriting my existing sheet I would get a #REF error because the link was broken. So I have worked my way around this for the list using the OFFSETSHEET Function:

VB:
Function SHEETOFFSET(offset, Ref)
[COLOR=#0000ff] ' Returns cell contents at Ref, in sheet offset[/COLOR]
Application.Volatile
With Application.Caller.Parent
SHEETOFFSET = .Parent.Sheets(.Index + offset) _
.Range(Ref.Address).Value
End With
End Function

This returns a value to a row in my mater sheet and I reference this for the data validation list.

However, I get the same problem when working with the HLookup function, the #REF error occurs. So far the only way I have figured out to work around this is to create another sheet that dynamically updates its values using the same OFFSETSHEET function, and my master sheet then references it.