Windows XP : Local Drive Mapping

In a cell, I've got

=UPPER(IF(ISNA(MATCH($E$3,'R:\Benefits\...\[BenDatabase.xls]Sheet1'!$A$1:$A$65536,0)),"",INDEX('R:\Benefits\...\[BenDatabase.xls]Sheet1'!$B$1:$B$65536,MATCH($E$3,'R:\Benefits\...\[BenDatabase.xls]Sheet1'!$A$1:$A$65536,1),0)))

& in VBA, I've got

Workbooks.Open Filename:= "R:\Benefits\...\BenDatabase.xls"

Ok when I'm in the office, but when I'm home, I want

=UPPER(IF(ISNA(MATCH($E$3,C:\Documents and Settings\...\[BenDatabase.xls]Sheet1'!$A$1:$A$65536,0)),"",INDEX('C:\Documents and Settings\...\[BenDatabase.xls]Sheet1'!$B$1:$B$65536,MATCH($E$3,'C:\Documents and Settings\...\[BenDatabase.xls]Sheet1'!$A$1:$A$65536,1),0)))

& Workbooks.Open Filename:= "C:\Documents and Settings\...\BenDatabase.xls"

ie, BenDatabase.xls is in different place, depending where I am. Been told can use Map Network Drive in some way to 'make' a place on home PC which has the filepath R:\Benefits\...\...\BenDatabase.xls so I can keep the formulas & code the same wherever I am.

Can you help?