PowerShell: Obtain Domain Admin Credential

This little snippet is reusable as an appendix to other scripts since Domain Admin access is required by many scripted operations.

# Check whether a given username matches the list of Domain Admins
function validateDomainAdminMembership{
    param (
        [string]$username
    )
    $matchedAdmin=$username -in $domainAdmins
    if($matchedAdmin){
        Write-Host "$username is a Domain Admin";
        return $True;
        }else{
       Write-Host "$username not a Domain Admin.";
       return $False;
       }
}

function testCredential{
  param (
      [string]$username,
      [string]$password
  )
  $plaintextPassword = (New-Object System.Management.Automation.PSCredential 'N/A',$providedPassword).GetNetworkCredential().Password
  $domainBindTest = (New-Object System.DirectoryServices.DirectoryEntry($domainObject,$username,$plaintextPassword)).DistinguishedName
  if ($domainBindTest){return $True;} else{Return $False;}
}

function obtainDomainAdminCred{
	$domainAdmins=(Get-ADGroupMember -Identity "Domain Admins" -Recursive | %{Get-ADUser -Identity $_.distinguishedName} | Where-Object {$_.Enabled -eq $True}).SamAccountName
  $global:cred=$False
  do {
    $providedID=Read-Host -Prompt 'Input a domain admin username'
    if (validateDomainAdminMembership $providedID){
      $providedPassword = Read-Host -assecurestring "Please enter the password"
      #$providedPassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($password))
      #$providedCredential = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $providedID,$providedPassword
      $goodCredential=testCredential -username $providedID -password $providedPassword
      if($goodCredential){
        "Domain Admin Credential validated!";
        $global:cred=New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $providedID,$providedPassword;
         #return $True;
         }
         else{   
         "Password doesn't match.";
         $global:cred=$False;
         #return $False;
         }
    }else{
    "Try again..."
    #return $False;
    }
  } until ($cred) 
}

function validateCurrentAccountAsDomainAdmin{
        if((whoami /groups) -match 'domain admins'){
        "This account is a Domain Admins member"; 
        return $True;
        }else{"This account is NOT a Domain Admins member";return $False;}
}

If(!(validateCurrentAccountAsDomainAdmin)){obtainDomainAdminCred;}