Hi,
In excel the cell contains: =Cnvrt2Weekly(A$3:B$166,H3)
Function has:
Option Explicit
Function Cnvrt2Weekly(src_date_val_tbl As Range, week_date As Variant)

'Assumes for src_date_val_tbl 1st column = source dates & 2nd column =source values
'Returns the value for a given week by finding in the source data the nearest dates
'one before & one after and their associated values. It then uses interpolation to calculate
'the value.

Dim SrcDates As Range, SrcValues As Range
Dim NumSrcRows As Long
Dim MatchDateRow As Variant

NumSrcRows = src_date_val_tbl.Rows.Count
Set SrcDates = src_date_val_tbl.Columns(1)
Set SrcValues = src_date_val_tbl.Columns(2)

Debug.Print "NumSrcRows: ", NumSrcRows
Debug.Print "Last Src Date: ", SrcDates.Cells(NumSrcRows)

'Use Match to find which source date (row) is just earlier than (above) the week date
MatchDateRow = WorksheetFunction.Match(week_date, SrcDates)
...

The problem is I get a runtime failure on the last line shown above.

All help is greatly appreciated!!!

Thank you,
Brent

P.S. also any hints on how to debug run time errors when the inputs to the function are ranges would be appreciated also!