Need to change the datasource of Data-Driven subscription using powershell

Question

I need to change the datasource of multiple ssrs data-Driven subscriptions using PowerShell. I have this code which can get the properties of data-Driven subscription but I need to fetch the datasource details first and then change it to also.

Here is my code.

function Get-DataDrivenSubscriptionProperties 
{
  param([string] $Subscriptionid, [object]$ssrsproxy) 
   $ddextensionSettings = $ddDataRetrievalPlan = $ddDescription = $ddactive = $ddstatus = $ddeventtype = $ddmatchdata = $ddparameters = $Null
    $ddOwner = $ssrsproxy.GetDataDrivenSubscriptionProperties($subscriptionid,[ref]$ddextensionSettings,[ref]$ddDataRetrievalPlan,[ref]$ddDescription,[ref]$ddactive,[ref]$ddstatus,[ref]$ddeventtype,[ref]$ddmatchdata,[ref]$ddparameters)
    [PSCustomObject]@{
        'Owner' = $ddOwner
        'extensionSettings' = $ddextensionSettings
        'DataRetrievalPlan' = $ddDataRetrievalPlan
        'Description' = $ddDescription
        'active' = $ddactive
        'status' =$ddstatus
        'eventtype' =$ddeventtype 
        'matchdata' = $ddmatchdata
        'parameters' = $ddparameters
      }
}

$ServiceUserPWD="************"
$ServiceUserName="Domain\UserName"

$DataSource = "/MyReports/EUROPE/M5EMPRDG"
$ReportFullPath = "/MyReports/EUROPE/rpt_Person";

$secpasswd = ConvertTo-SecureString "$ServiceUserPWD" -AsPlainText -Force
$mycreds = New-Object System.Management.Automation.PSCredential ($ServiceUserName, $secpasswd)

$ssrsServer = "https:/myserver/Reportserver";
$ssrsProxy = New-WebServiceProxy -Uri "$($ssrsServer)/ReportService2010.asmx?WSDL" -Credential $mycreds;

# Get the report subscriptions
$subscriptions = $ssrsProxy.ListSubscriptions($ReportFullPath)

foreach ($sub in $subscriptions)
{

        if($sub.isdatadriven -eq 'true')
        {
          $subprops += Get-DataDrivenSubscriptionProperties -subscriptionid $sub.SubscriptionID -ssrsproxy $ssrsProxy
          $sub | add-member -MemberType NoteProperty -Name Properties -value $subprops -TypeName [PSCustomObject]
        }
}

Till here I can write this code, but in this $sub there is no details of datasource so I am not able to change the datasource.

Please help to give me complete code to get the datasource and change the datasource of data-driven subscription.

thank you.