Hi Ryan,
There is no property to acheive this. But you can do it by applying different mask while in editting mode and also you need to handle the MaskCustomValidate event of the MaskEditControl of the cell. And to display the negative sign in the normal mode, you can use the DrawCellDisplayText event.
Please refer to this sample.
http://websamples.syncfusion.com/samples/Grid.Windows/F61629/main.htmBest Regards,
Saravanan