Error with VLookup Formula

Hi,

I am using a formula that is working great with looking up numerical "item number" in my spreadsheet.
Come to Alpha and Numerical 'item numbers" i get a #N/A Error.

This is the formula I'm using

=VLOOKUP(A27,'Totals Scanned'!$A$2:$C$310,3,FALSE)

Can someone please shed some light.... your help would be greatly appreciated!

I have attached a sample of my worksheet.... The error is occuring on the Pronto - Variance Sheet (sheet4),
i need a formula that can match both number and letter values so that i dont have to change the formula based on the item number... needs to be automatic and flowing!