title: Allow only Negative number in CXGrid
body: <p>Im working in Delphi 2006 with devexpress.</p>
  
  <p>I have a cxGrid. I want to restrict the entry of values for a negative number column,</p>
  
  <p>my probleme is how can I test the position of '-' when adding it the cell</p>
  
  <p>Is some simple way to allow only negative number in the cell of cxgrid.</p>
  
  <p>thanks in advance</p>