Highlight the value of Input Field in webDynpro ABAP

Created Three input fields in Webdynpro named as Input1, Input2, Input3. Those were binding with three context attributes named formula1, formula2 and formula3 respectively.

In the method, WDDOINIT doing calculations such as follows formula3 = formula1 - formula2. If the formula3 value was negative, i need to highlight text / field(red Color) Input3 field in portal side (No Need to show any error message).

Help will be appreciated.