[NEWFIELD] = val( [OLDFIELD] )
转自：http://forums.esri.com/Thread.asp?c=93&f=992&t=75372
its all the details of exactly what the field your number-text is in and exactly what the field your final number is going to. I have sucessfully converted a field of type=string length=4, precision=0, scale=0 to a field of type=long, length=8, precision=8,
scale=0 with the [NEWFIELD] = val( [OLDFIELD] ) in the map field calculator.