$ofd = New-Object System.Windows.Forms.OpenFileDialog
$ofd.Filter = "PFX file (*.pfx)|*.pfx|All files (*.*)|*.*"
$ofd.Multiselect = $false
$ofd.CheckFileExists = $false
#$ofd.FileName = "config.json"
$res = $ofd.ShowDialog()
if ($res -eq [System.Windows.Forms.DialogResult]::OK) {
    if ($ofd.FileName) { $filePath = $ofd.FileName}
}

Import-ExchangeCertificate -Server $env:COMPUTERNAME -FileData ([System.IO.File]::ReadAllBytes($filePath)) -Password (Get-Credential -Message "Enter PFX password" -UserName "dummy").password