Change the Selected text to Upper Case

Hi, I have the below to code to select the Paragraph. But after that I need to update the selected text to UPPER CASE. Please help me getting the code for this.

var doc = app.ActiveDoc;
var flow = doc.MainFlowInDoc;
var textFrame = flow.FirstTextFrameInFlow;
var pgf = textFrame.FirstPgf;
var textRange = new TextRange ();
textRange.beg.obj = pgf; 
textRange.beg.offset = 0; 
textRange.end.obj = pgf; 
textRange.end.offset = Constants.FV_OBJ_END_OFFSET;
doc.TextSelection = textRange;

//Para got selected now i need change the paragraph to UPPERCASE without disterbing other formats