Need help wit the "DoCmd.OpenForm"

[June7]

The VBA procedure should be a Sub and the parameter must be concatenated outside quote marks like shown in original post. The converted code is button click event not listbox click as in original post. Converted code references field not listbox as parameter.

[davegri]

I don't know what a trusted location is

I suspect that's the reason that my DB, Your DB and any DB that you create or try to use in the future will not work with VBA.
Have a look at this:
https://support.office.com/en-us/art...3-4e7c67147fb4

[CJ_London]

this

Function cmdTestListClick()


should

a) be in the form module
b) should look like Private Sub cmdTestList_Click()

the fact it doesn't implies you have created the macro as a general macro and not one directly connected to the control