javascript validation to check correct string format

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C#

var _selOGC = document.getElementById('<%= this.txtOGCCommand.ClientID %>').value;
           var _ogc = _selOGC.indexOf("$IT+");
           if (parseInt(_ogc) != 1)
           {
               alert ('<%= this.GetGlobalResourceObject("resOGCommand","validOGC") %>');
               document.getElementById('<%= this.txtOGCCommand.ClientID %>').focus();
               //return false;
           }

i ve a module named ogc wen i add some junk other than "$IT+" it will pop up a msg saying please add valid ogc
wen i add proper format and save it ll display same pop up msg but the data will be saved.
where m i going in the script?