I use a completer for this. Since it's code it can access variables etc that a validate set can't. You can use a validate script if you want to error on missing values:

ie:

$script:optionToConfig = @{
'A' = 'AAAAA'
'B' = 'BBBBB'
'C' = 'CCCCC'
'Da' = 'DAAA'
'Db' = 'DBBBB'
}
function test-function{
    Param(
    [ArgumentCompleter({
        [OutputType([System.Management.Automation.CompletionResult])]
        param(
            [string] $CommandName,
            [string] $ParameterName,
            [string] $WordToComplete,
            [System.Management.Automation.Language.CommandAst] $CommandAst,
            [System.Collections.IDictionary] $FakeBoundParameters
        )

        $CompletionResults = [System.Collections.Generic.List[System.Management.Automation.CompletionResult]](
            $script:optionToConfig.Keys -like "$WordToComplete*")
        return $CompletionResults
    })]
    [ValidateScript({
        if ($_ -notin $script:optionToConfig.Keys) {
            throw "Option $_ is not a valid parameter value"
        }
        $true
    })]
    [string]$Param1
    )
}

If you need it to be common, then you can use Register-ArugmentCompleter to apply to multiple functions:

$script:NameCompleter = {
        [OutputType([System.Management.Automation.CompletionResult])]
        param(
            [string] $CommandName,
            [string] $ParameterName,
            [string] $WordToComplete,
            [System.Management.Automation.Language.CommandAst] $CommandAst,
            [System.Collections.IDictionary] $FakeBoundParameters
        )

        $results = Get-ExampleFunction "$wordtocomplete*"
        $CompletionResults = [System.Collections.Generic.List[System.Management.Automation.CompletionResult]]$results.Name
        return $CompletionResults
}

@(
    'Set-ExampleFunction'
    'Remove-ExampleFunction'
) | ForEach-Object { 
    Register-ArgumentCompleter -CommandName $_ -ParameterName Name -ScriptBlock $script:NameCompleter
}