Make a signature change the color of a submit button

Hello,

I'm trying to make a Submit button turn green after a digital signature is applied, but no luck.  I have tried entering the script below in the form:ready, layout:ready and docready events of the button, as well as in the"form1".  Of course, when I put the scripts in the "form1" object, "this" gets changed to the full button name.  Nothing works.  Any suggestions?  Thanks.

var oState = event.target.getField("form1[0].Page2[0].SupervisorReview[0].SecondBlock[0].SupervisorSignature[0]").signatureValidate()
if (oState == "1")  {  this.fillColor = "0,128,0"; //green fill  this.caption.font.fill.color.value = "255,255,255"; //white font  }