Get Next date based on textbox entry days

Hai all,

i have 3 textboxes - Txtcurrntdate,Txtdays, TxtNxtDate

in TxtCurrntdate i select currntdate or previous or next day date, after entering days in txtcurrntdate i want add those days in to currnt date textbox and i want  automatically get nextdate in TxtNxtDate.

if any body understand my query please help me

Thanks in advance