Everyone,

I sort by a unique identifier (a concatenation of two codes). This is an example:
1-7SM2AZ-OISTEAM12O

The original formula is this:
=IF($A11="","",INDEX('Siebel Pull - Do not update'!B$3:B$1044,MATCH('Input Data here'!$A11,'Siebel Pull - Do not update'!$AC$3:$AC$500,0),1))

Basically, its saying:
IF the cell we will look in is blank, leave this entry blank
Otherwise do an index match on another sheet.

However, when we sort the unique identifier column with an A-Z sort, the formula changes in the middle but not the first part:
=IF($A11="","",INDEX('Siebel Pull - Do not update'!B$3:B$1044,MATCH('Input Data here'!$A336,'Siebel Pull - Do not update'!$AC$3:$AC$5000,0),1))

Why the heck is this happening???

Thanks!