Make a words Sentence Case?

Here's my script so far.  WHere the Grep style changes is i would like to use all the grep styles i have in indesign.  Or if possible certain ones. the replace will have a ton more by the time i;m done but again the Grep is what i really need help with.

//DESCRIPTION: Running changes.

//Replace("<CR>", "Return") 

//~  Created by Chris Bishop - (5-3-16)  

    Replace(" <CR> ", "^p") 

    Replace("  ", " ")

    Replace(" :", ":")

    Replace(" .", ".")

    Replace("^p^p", "^p")

    Replace(" <CR>", "^p")

        function Replace(input, output) 

        { 

            app.selection[0]; 

            app.findTextPreferences = app.changeTextPreferences = NothingEnum.nothing; 

            app.findTextPreferences.findWhat = input; 

            app.changeTextPreferences.changeTo = output; 

            app.activeDocument.changeText(); 

        } 

//~     Grep Style Changes

//~  THe alert message shown when running this script. 

try{ 

    do { 

        myText.pointSize = myText.pointSize - .01; 

        } while (myTextFrame.overflows == true); 

    } 

catch(e){ 

    alert("Text already Formatted")