>how can i disable my keyboard except the digits,"-"negative sign and the enter keys?

One approach is to use the following in the KeyPress() event of the control:

LPARAMETERS nKeyCode, nShiftAltCtrl

* We only accept digits and - sign
IF NOT ((nKeyCode>=48 AND nKeyCode<=57) OR nKeyCode=45)
   NODEFAULT
   RETURN
ENDIF

However, this is only a start. Because, I assume you would like to allow the user to type the required keys to go back, delete, use the arrows, etc.

There are probably better approaches. Using the Format property is probably one of them.