Formula Cell References Change When Sorting After Filtering

Morning everyone,

I have two worksheets, parts of which i've included below. In Worksheet A a profile code is entered into the 'Profile' column and a millimetre width is entered into the 'Width' column. I need a formula to be entered into the 'Manufacturing Code' column which would access the table shown in Worksheet B, cross-referencing the profile code and the width entered to give the manufacturing code.

Upon seeking help before I have arrived on the formula shown below:

=INDEX(wsB!$B$2:$J$5,MATCH(wsA!$C2,wsB!$A$2:$A$5,0),MATCH(wsA!$D2,wsB!$B$1:$J$1,0))

This works exactly how I'd want it to, right up until I need to sort any of the columns. Then, the two cell references wsA!$C2 and wsA!$D2 do not change correctly relative to the row the formula is now in after the sort. I can see from this site and others that this is a common issue with Excel '07?

Does anyone know of a way around this?

Thanks a lot,

Rob Mitchell