reducing formula size

Hi,
I have a formula that looks at another file to get a number of things. The only problem is that the formula is now over 255 characters, so I cannot update the filename link as the formula is too long. Is it possible to either:
1. pass the filename as a variable name (to reduce the formula length)
2. Write this formula in a shorter way (in not adept at VBA yet).

The formula is:

=IF(ISNA(INDEX('P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$1:$65536,MATCH($G8,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$A:$A,0),MATCH(Q$6,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$4:$4,0),1)),0,INDEX('P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$1:$65536,MATCH($G8,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$A:$A,0),MATCH(Q$6,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$4:$4,0),1))+IF(ISNA(INDEX('P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$1:$65536,MATCH($G8,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$A:$A,0),MATCH(Q$6,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$5:$5,0),1)),0,INDEX('P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$1:$65536,MATCH($G8,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$A:$A,0),MATCH(Q$6,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$5:$5,0),1))/(52/12)

or if you want to make some sense out of it:

=IF(ISNA(
INDEX(
'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$1:$65536,MATCH(
$G8,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$A:$A,0
),MATCH(
Q$6,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$4:$4,0
)
,1)
)
,0,
INDEX(
'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$1:$65536,MATCH(
$G8,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$A:$A,0
),MATCH(
Q$6,'P:\Operating Statement\Payroll\[Week 45 0607 NAM.xls]Units'!$4:$4,0
),1
))

+IF(
ISNA(
INDEX(
'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$1:$65536,MATCH(
$G8,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$A:$A,0
),MATCH(
Q$6,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$5:$5,0
),1
)
)
,0,
INDEX(
'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$1:$65536,MATCH(
$G8,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$A:$A,0
),MATCH(
Q$6,'P:\Operating Statement\Payroll\[Month 11 0607 NAM.xls]Units'!$5:$5,0
),1
))
/(52/12)

Thanks in advance.