validate your fields if they are null or empty don't include them

for example
SQlString ="select * from table "
SQlString = SQLString + "where LastName = '" & txtLastName & "',"
if trim(txtFirstName) <> "" then
	UpdateSQL = UpdateSQL & " FirstName = '" & txtFirstName & "',"
end if
etc etc
until you reach all field
you need a variable on top to know which fields is last to ommit the last
comma
good luck