Since we can't look over your shoulder, you will have to troubleshoot the problem yourself. mdmackillop showed you a trick to view your string for the Indirect() function. The link that I gave showed the syntax.

In my A6:
C:\Bill\04895087\2010-April\BillRecovery\Files\Mob-04-2010-100642.xls
I saved a file with name t:\test\Mob-04-2010-100642.xls and opened it. I did not have a sheet named Recovery so I used Sheet1. The path is not the same but Excel only allows one file with the same name to be open at once.

To check my formula: ="'" & "[" & RIGHT(A6, 22) & "]Sheet1'!$C$7"
Which resolves to: '[Mob-04-2010-100642.xls]Sheet1'!$C$7

The Indirect formula is then: =Indirect("'" & "[" & RIGHT(A6, 22) & "]Sheet1'!$C$7")

If I close Mob-04-2010-100642.xls, nothing is changed with the Indirect() value until a recalculation happens which will then show #REF.