There are other ways to do this as well. You could create 2 arrays with the corresponding index (which is similar to what Howard's hash function is doing).

code:
$CCentre_Share = "I:","Q:","R:","U:","V:","X:","Y:"
$CCentre_Drive = "\\FAIRY\DESSERT","\\IO\XCRIPT","\\IO\INTRANET",
"\\CUSTBAK\DATA","\\HAL\DATA","\\CUSTBAK\DATA","\\HAL\DATA","END"

If Ingroup("MMGroup\CCOpsX")=1
$counter = 0
While $CCentre_Drive[$counter] <> "END"
USE $CCENTRE_DRIVE[$counter] $CCENTRE_SHARE[$counter]
.
.
.
.
This should work.. also you could do something like subsituting for this:
USE $CCentre_Drive[$Counter]

code:
$drivemap = $CCentre_Drive[$Counter]
EXECUTE("USE $drivemap")
....

I haven't tested this second code. You might need to enclose your declarations in single quotes like:

$CCentre_Drive[1] = "I: '\\FAIRY\DESSERT'"

Or it may work fine as-is.
Brian