how to make a entry field blank

suppose I have a button that I put a code to make the an entry field
(?field1) blank ,  so when after key in some character in the entry
field(?field1), but when I push this button all the key-ed in character
in the entry field will be blanked, so I can entry the new character in
the entry field, how to write the code for empty the entry field ?
Any assistance is appreciated.


thank. bob