automatic date insert

automatic date insert

hello,
 
there are 2 fields in my newform.aspx. 'Problem'(dropdown list with values test1, test2) and 'Solution Date'.
i want to auto fill the field 'Solution Date' depending on the value of the dropdown list.
test1: solution date= current date + 2 days
test2: solution date= current date + 5 days
 
i don't know how to write the current days + days into the field 'Solution Date'.
 
can somebody help me?
 
thanks