chkBox driving me mad

[A real begineer]

Okay, I thought this was really simple, but there must be something Iam not seeing.

QryResults lists the results for an individual client. For every third result I want chkClarifier to be true, that is enable dose.

This code should set chkClarifier to true on every third record but it is not firing correctly.

I have this code set on the command button to open the report.


Dim sngA As Single
Dim sngB As Single

sngA = DLookup("[ID]", "[qryResults]", "[Clarifier]=True")
sngB = DLookup("[ID]", "[qryResults]")
If sngB - sngA >= 3 Then
chkClarifier = True
End If