Need the syntax for c drive free percentage on servers - Using power shell

Hi Friends,

I could find some ps script with gui option for server health check. It has its grid view and displays server parameters like uptime, last boottime, Service pack etc. So I was trying to add c drive free percentage parameter and last hotfix date also into this. I have attached the parameters syntax part (main part from the whole script) below and it contains my syntax for c drive free percentage as well, but didn't work. Since am very new to PS i have failed to make it successful :( 

Request you to help me with your ideas to fix it (I have hashed and highlighted my syntax)

Please feel free to revert for any questions

if ($os) {
                    #clear OS if it has a left over value
                    Clear-Variable os
                }
                 $os=Get-OS $computer
               if ($os) {
                   $lastboot=$os.ConvertToDateTime($os.lastbootuptime)
                   Write-Debug "Adding $lastboot"
                   uptime=((get-date) - ($os.ConvertToDateTime($os.lastbootuptime))).tostring()
                   Write-Debug "Adding $uptime"
                   #$HotFix=Get-HotFix | Select-Object installedOn -last 1 | Sort-Object -Property installedOn -Des
                   #Write-Debug "Adding $HotFix
                   
                   #$drive=Get-WmiObject -Class win32_Volume -ComputerName $computername -Filter "DriveLetter = 'C:'" |
                   #Select-object @{Expression = {“{0:N2}” -f  (($_.FreeSpace / $_.Capacity)*100) } } 
                   #Write-Debug "Adding $drive"
                   $osname=$os.Caption
                   Write-Debug "Adding $osname"
                   $servicepack=$os.CSDVersion
                   Write-Debug "Adding $servicepack"
                   
                   $obj | Add-Member Noteproperty OS $osname
                   $obj | Add-Member Noteproperty ServicePack $servicepack
                   $obj | Add-Member Noteproperty Uptime $uptime
                   $obj | Add-Member Noteproperty LastBoot $lastboot
                  #$obj | Add-Member Noteproperty Last Windows update $HotFix
                   #$obj | Add-Member Noteproperty System Drive $drive
               }
               else {
               Write-Debug "Setting properties to N/A"
                   $obj | Add-Member Noteproperty OS "N/A"
                   $obj | Add-Member Noteproperty ServicePack "N/A"
                   $obj | Add-Member Noteproperty Uptime "N/A"
                   $obj | Add-Member Noteproperty LastBoot "N/A"
                  #$obj | Add-Member Noteproperty Last Windows update "N/A"
                   #$obj | Add-Member Noteproperty System Drive "N/A"
               }
          }
          else {
                Write-Debug "Ping failed"
                Write-Debug "Setting properties to N/A"

               $obj | Add-Member Noteproperty Pinged "No"
               $obj | Add-Member Noteproperty IP "N/A"
               $obj | Add-Member Noteproperty OS "N/A"
               $obj | Add-Member Noteproperty ServicePack "N/A"
               $obj | Add-Member Noteproperty Uptime "N/A"
               $obj | Add-Member Noteproperty LastBoot "N/A"
               #$obj | Add-Member Noteproperty Last Windows update "N/A"
               #$obj | Add-Member Noteproperty System Drive "N/A"
          }
        
         #Add the object to griddata
             Write-Debug "Adding `$obj to `$griddata"
             $griddata+=$obj