Messagebox return value and javascript

hi to allplz i have this problem , i have an agent LS that i want to modify the old code to web enable , this is the code that i cant convert to JS

here is the code

If Messagebox(Doc.ColumnValues1),4+32+256,DocTitle.ColumnValues(1)) =7 Then

DisplayWarningMsg = 0  

Else

DisplayWarningMsg = 1