One vlookup returns correct value, next does not

Hi All,

Looking for some help to figure out what is causing our problem. My friend has created the attached excel sheet in Excel 2003. The issue is that the a vlookup does not seem to be finding the correct line for the value from the lookup table when it is returned twice.

Let me explain - The details are contained in the attached workbook. There are three sheets in the workbook - NH3Curve, Samples and Qvalue table.

On the Samples sheet, in cell C12 and C13 you can enter varying values. Go across to F12 and F13 and you will see that they both have the value 22.1. This is where the issue occurs - in cells G12 and G13 the lookup value should be the same - but it is not. G12 is actually returning the value for 22.0 not 22.1. (lines 173 and 174 on the Qvalue sheet). We cannot ferret out why this is happening.

Any help would be greatly appreciated. Sometimes when you look at something you can't see the obvious, so I hope it is that simple.

I have not cross-posted this topic anywhere else.

Thanks for your time.