Sumproduct vs Countif

Hi,

I have a "If(countif(..." that counts the number of times a persons name appears on an external workbook. Then if the count if returns a value greater than 1, 2, etc..., I then use an index to get some data.

However, the countif will not work unless the sheet it is counting off of is open?

Is there another way, perhaps using a sumproduct, that will allow me to find the number of times a persons name appears on a sheet?

=IF(COUNTIF('[Jan 10 - Acton - Group 3.xls]Week 41'!$F$4:$F$50,$B22)>=1,INDEX('[Jan 10 - Acton - Group 3.xls]Week 41'!$F$4:$W$50,MATCH($B22,'[Jan 10 - Acton - Group 3.xls]Week 41'!$F$4:$F$50,0),18)/100, "")

Above is the formula I am using