dataverse_lookup_bind.ps1

$environmentUrl = "https://yourorg.crm.dynamics.com"
$accessToken = "YOUR_ACCESS_TOKEN"
$contactId = "CONTACT_GUID"
$accountId = "ACCOUNT_GUID"

$headers = @{
    Authorization       = "Bearer $accessToken"
    Accept              = "application/json"
    "Content-Type"     = "application/json"
    "OData-Version"    = "4.0"
    "OData-MaxVersion" = "4.0"
}

$body = @{
    "parentcustomerid_account@odata.bind" = "/accounts($accountId)"
} | ConvertTo-Json

Invoke-RestMethod -Method Patch -Uri "$environmentUrl/api/data/v9.2/contacts($contactId)" -Headers $headers -Body $body | Out-Null
Write-Host "Linked contact $contactId to account $accountId"