Problem with datediff in textbox validation

[April15Hater]

Hi-

I'm having trouble getting a validation rule to work. My textbox (txtTimeOutDate) is allowing values that are not valid.

<=[Forms]![frmHoursTracking]![cboWeekEnding] And
 >=([Forms]![frmHoursTracking]![cboWeekEnding]-6) And 
DateDiff("d",[txtTimeOutDate],[txtTimeInDate])<=1

The DateDiff is what is in question. I'm trying to keep users from entering more than one day between txtTimeOutDate and txtTimeInDate and it is allowing those values. I have a feeling it is because I'm referencing [txtTimeOutDate] in it's own validation. If that's the case is there a way around that?

Thanks,

Joe