What is the correct way to create a mask for decimal numbers in Windows Forms?

$txtValue = New-Object System.Windows.Forms.MaskedTextBox

Using the mask $txtValue.Mask = "999,999,999.9999" doesn't allow me to enter, for example, 1.333 without typing 000,000,001.333 (or clicking directly at the correct position, but that's impractical). The mask $txtValue.Mask = "000,000,000.00" has almost the same issue.

I tried adding event functions, but it only edits the first number and fails:

$txtValue.add_TextChanged({ 
    $mytxt = $txtValue.Text 
    $txtValue.remove_TextChanged($thisEvent) 
    $myValue.Text = [double]::Parse($mytxt)
    $txtShareValue.add_TextChanged($thisEvent)
})

I also tried using the regex [^0-9.] and slicing the range if the text exceeds the length limit during an event, but this doesn't prevent entering multiple consecutive periods.