$ResourceGroupName=""
$LoadBalancerName=""
$BackEndPoolName=""

$LoadBalancer = Get-AzLoadBalancer -Name $LoadBalancerName -ResourceGroupName $ResourceGroupName
$Probe=Get-AzLoadBalancerProbeConfig -Name "probeA" -LoadBalancer $LoadBalancer
$BackendPool = Get-AzLoadBalancerBackendAddressPool -ResourceGroupName $ResourceGroupName -LoadBalancerName $LoadBalancerName -Name $BackEndPoolName

$LoadBalancer | Set-AzLoadBalancerRuleConfig -Name "Rule1" -FrontendIPConfiguration $LoadBalancer.FrontendIpConfigurations[0] -Protocol "Tcp" -FrontendPort 80 -BackendPort 80 -BackendAddressPool $BackendPool -Probe $Probe
$LoadBalancer | Set-AzLoadBalancer