I think the Dcount is what you are looking for. The syntax is similar to a Dlookup. Here is an example.
If DCount("[JobNumber]", "TimeGR", "[JobNumber]= '" _
& strInput & "'") = 0 Then
' Do something here ....
If DCount("[FieldName]", "TableName", "[FieldName]= '" & Criteria & "'") >...