I believe that I got this to work correctly by using the following example which uses the TextChanged event of the textbox.
method-id textBox1_TextChanged final private.
procedure division using by value sender as object e as type System.EventArgs.
*>Remove previous formatting, or the decimal check will fail including leading zeros
declare myvalue as string =
textBox1::Text::Replace(",", "")::Replace("$", "")::Replace(".", "")::TrimStart('0')
declare ul as decimal
*>Check we are indeed handling a number
if type Decimal::TryParse(myvalue, ul)
set ul to ul / 100
*>Unsub the event so we don't enter a loop
invoke textBox1::remove_TextChanged(new System.EventHandler(self::textBox1_TextChanged))
*>Format the text as currency
set textBox1::Text to type
String::Format(type System.Globalization.CultureInfo::CreateSpecificCulture("en-US"), "{0:C2}", ul)
invoke textBox1::add_TextChanged(new System.EventHandler(self::textBox1_TextChanged))
invoke textBox1::Select(textBox1::Text::Length, 0)
end-if
declare goodToGo as condition-value = self::TextisValid(textBox1::Text)
if not goodToGo
set textBox1::Text to "$0.00"
invoke textBox1::Select(textBox1::Text::Length, 0)
end-if
goback.
end method.
method-id TextisValid private.
procedure division using by value mytext as string
returning ret-bool as condition-value.
declare money as type System.Text.RegularExpressions.Regex =
new System.Text.RegularExpressions.Regex("^\$(\d{1,3}(\,\d{3})*|(\d+))(\.\d{2})?$")
set ret-bool to money::IsMatch(mytext)
goback.
end method.