Hi ArviL
Thank you again for your explanations and recommendations. There is a lot of work in implementing your ideas, but I will get to it.
I have noticed that the MachineNo field in the xServices table actually has a space in it. Hence the space in the code below. (yet something else to clean up)
I've adapted the code you suggested, but get an error when trying to save it. The expression you entered contains an invalid string
Code:
=DMax("[HourMtr]", "xServices", "[Machine No] = '" & Forms!frmMachineComponents!txtMachineNo & "'" AND [HourMtr] >0")
I really do appreciate your help.