Azure – Automate express route circuit gateway based on express route circuit provision status

I want to create express route gateway based on express route circuit provision status using terraform . When express route circuit is created initial provider status will be unprovisioned. once it is provisioined in equinix portal this status changes to provisioned.To change this status, it would take few days,till then express route gateway need not be created as it a bit expensive resource.when i run pipeline, initially express route circuit will be created and it’s status will be unprovisioned, now in this state express route gateway creation should be skipped. When the status is changed to provisioned, I will run the pipeline , here it has to check the provision status only when changed to provisioned, express route gateway should be created .

 resource "azurerm_resource_group" "example-express-rg" {
  name     = "example-vnet-rg"
  location = "West Europe"
}

resource "azurerm_virtual_network" "vnettest" {
  name                = "example-vnet"
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.example-express-rg.location
  resource_group_name = azurerm_resource_group.example-express-rg.name
}

resource "azurerm_subnet" "gateway_subnet" {
  name                 = "GatewaySubnet"
  resource_group_name  = azurerm_resource_group.example-express-rg.name
  virtual_network_name = azurerm_virtual_network.vnettest.name
  address_prefixes     = ["10.0.1.0/24"]
}

resource "azurerm_public_ip" "publicip" {
  name                = "example-public-ip"
  location            = azurerm_resource_group.example-express-rg.location
  resource_group_name = azurerm_resource_group.example-express-rg.name
  allocation_method   = "Static"
  sku                 = "Standard"

}

resource "azurerm_resource_group" "expressrg" {
  name     = "exprtTest"
  location = "West Europe"
}
resource "azurerm_express_route_circuit" "expressr" {
  name                  = "expressRoute1"
  resource_group_name   = azurerm_resource_group.expressrg.name
  location              = azurerm_resource_group.expressrg.location
  service_provider_name = "Equinix"
  peering_location      = "Singapore"
  bandwidth_in_mbps     = 1000

  sku {
    tier   = "Standard"
    family = "MeteredData"
  }

  tags = {
    Purpose = "Resource"
    ResorceOwner ="CCTeam"
  }
}

# Data Source to Check the Status of the ExpressRoute Circuit
data "azurerm_express_route_circuit" "expressr_status" {
  name                = azurerm_express_route_circuit.expressr.name
  resource_group_name = azurerm_resource_group.expressrg.name
}
# Virtual Network Gateway (Create Conditionally)

resource "azurerm_virtual_network_gateway" "example" {
  depends_on = [azurerm_express_route_circuit.expressr]
  count               =data.azurerm_express_route_circuit.expressr_status.service_provider_provisioning_state == "Provisioned" ? 1 : 0
  name                = "testgw"
  location            = azurerm_resource_group.example-express-rg.location
  resource_group_name = azurerm_resource_group.example-express-rg.name
  type     = "ExpressRoute"
  vpn_type = "PolicyBased"
  sku           = "Standard"

  ip_configuration {
    name                          = "vnetGatewayConfig"
    public_ip_address_id          = azurerm_public_ip.publicip.id
    private_ip_address_allocation = "Dynamic"
    subnet_id                     = azurerm_subnet.gateway_subnet.id
  }
  
  tags = {
    Purpose = "Resource"
    ResorceOwner ="CCTeam"
  }
}

I tried using data block and condition but it results with error

Error: Invalid count argument
│
│ on main.tf line 75, in resource "azurerm_virtual_network_gateway" "example":
│ 75: count =data.azurerm_express_route_circuit.expressr_status.service_provider_provisioning_state == "Provisioned" ? 1 : 0
│
│ The "count" value depends on resource attributes that cannot be determined until apply, so Terraform cannot predict how
│ many instances will be created. To work around this, use the -target argument to first apply only the resources that the
│ count depends on.

Please suggest me on this .