Lookup not picking up negative numbers

Ok this is strange.

I am using lookup and I had to change the Date option to 1904 so as I could view the negative time instead of a bunch of ###### signs. Now I have the negative numbers showing for example.. -00:21:00. I have added this to the Lookup table I created but it will not find them. It finds all the positive numbers and puts the appropriate value in the cell. As soon as the number is negative it gives me an N/A. Any Ideas

What lookup formula are you using?

How are the times generated, if by formula then what's that?