Question Subform issues linking tables (1 Viewer)

I'm having an issue linking data into a field in a subform.

I have a business which has many jobs. We have accelerometers which are used for each job (ranging from 10-80).

As seen by the attachment there are a few one to many relationships based on this.

I've created the form attached and subform based on the JobAccs table. I'd like to be able to pull data for the accelerometer SN/type/sensitivity etc once I enter the accelerometer cable number in the subform as seen from the screenshot.

I've tried using the following in the control source section of SN in the subform:

=DLookUp("[SN]","[Accelerometers]","[Accelerometers]![Cable Number]=[Cable Number]")

But this just brings up the same number every row when it should link to the correct SN of the accelerometer cable number I entered!

Any ideas???

Thanks

This should help:

http://www.theaccessweb.com/general/gen0018.htm

This may also apply:

http://www.baldyweb.com/Autofill.htm