Matrix Cell cancel change

Hi,

Who knows how to cancel a validate on a Matrix cell

I'm tried with bubbleevent = false but the column is still going to the other one.

For instence, I'm on the Unit Price in the detail of a Sales Order. I'm able to get the value of the cell beeing modified but if the user doesn't enter the right one, I would like to STAY on that cell not going anywhere until the user enter the right value.