Fred,

You problem may reside in this line;

if rtrim(Users.Password) = rtrim(thisform.txtPassword.value)

The problem is that if rtrim(thisform.txtPassword.value) evaluates to the empty string ( "" ) then this IF will always be True as the empty string on the right sode of an = is equal to everything you could possibly put on the left side. I would rephrase this IF to;

if Users.Password == PADR(ALLTRIM(thisform.txtPassword.value),LEN("Users.Password"))

This expression will remove all leading and trailing spaces from the textbox value and then pad it on the right siode with spcaes to be of equal length as the field in the table. Then is uses the == operator for exact equality comparison.