CFL Window

I am having two matrix in my screen.. In the first matrix document numbers loaded in the first column...... In the second matrix item loaded in the first column....... In the first matrix, without selecting tab cfl, when i entered the document number and press tab corresponding details will be loaded in the other columns...... but in the item matrix when i enter the item as "item01" ( this is available in the item cfl) and press the tab means, a new CFL window opens..... Wat the reason...?