A quick direct conversion is:
Code:
$TRUE=Not 0
$FALSE=Not $TRUE
 
$UndoScopeID1 = $Application.BeginUndoScope("Define Custom Properties")
$vsoShape1 = $Application.ActiveWindow.Page.Shapes.ItemFromID(2)
$intPropRow2 = $vsoShape1.AddRow($visSectionProp, $visRowLast, $visTagDefault)
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsLabel).FormulaU = '"Property1"'
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsType).FormulaU = "0"
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsFormat).FormulaU = '"@@"'
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsLangID).FormulaU = "1033"
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsCalendar).FormulaU = ""
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsPrompt).FormulaU = ""
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsValue).FormulaU = '"Value1"'
$vsoShape1.CellsSRC($visSectionProp, $intPropRow2, $visCustPropsSortKey).FormulaU = ""
$Application.EndUndoScope($UndoScopeID1, $TRUE)


However, there are a number of variables or enumerations which you didn't include in your code sample, so I don't know if you have defined them elsewhere in your script.