PrecisionScaleExtender

	ko.extenders.precisionScale = function (target, dynamicProperty) {
		//create a writable computed observable to intercept writes to our observable
		var result = ko.pureComputed({
			read: target,  //always return the original observables value
			write: function (newValue) {
				var current = target();
				var valueToWrite = newValue;

				if (valueToWrite) {

					//get precision and scale
					var precision = dynamicProperty.ColumnPrecision;
					var scale = dynamicProperty.ColumnScale;

					//turn into string and parse
					var valAsString = valueToWrite.toString();
					var parts = valAsString.split('.');
					var integerPartString = parts[0];
					var fractionalPartString = parts[1];
					
					//store negative info
					var isNegative = integerPartString.indexOf('-') > -1;
					if (isNegative)
					integerPartString = integerPartString.replace('-','');

					//remove non alpha numeric
					integerPartString = integerPartString ? integerPartString.replace(/\D/g, '') : '';
					fractionalPartString = fractionalPartString ? fractionalPartString.replace(/\D/g, '') : '';

					//get maximum lengths based on precision and scale
					var maxIntegerPartLength = precision - scale;
					var maxFractionalPartLength = scale;

					//get attempt lengths
					var attempedIntegerPartLength = integerPartString ?  integerPartString.length : 0;
					var attempedfractionalPartLength = fractionalPartString ? fractionalPartString.length : 0;

					//truncated parts if needed
					if (attempedIntegerPartLength > maxIntegerPartLength) {
						integerPartString = integerPartString.substr(0, maxIntegerPartLength);
					}
					if (attempedfractionalPartLength > maxFractionalPartLength) {
						fractionalPartString = fractionalPartString.substr(0, maxFractionalPartLength);
					}

					//put the whole value back together								
					var formattedValue = integerPartString;
					if (fractionalPartString)
						formattedValue = integerPartString + '.' + fractionalPartString;
					if (isNegative)
						formattedValue = '-' + formattedValue;

					valueToWrite = formattedValue;

				}
				
				//if the formatted value is the same force a refresh
				if (newValue !== current) {
					target('');
				}
				target(valueToWrite);
			}
		}).extend({ notify: 'always' });

		//initialize with current value to make sure it is rounded appropriately
		result(target());

		//return the new computed observable
		return result;
	};