Help, signatureValidate() function doesn't work on hidden fields

Question

I am trying to use the signatureValidate() function to check if any signature fields are signed. I am doing this because I need to have the signature fields lock the form manually so that a specific department can make changes after signatures have been applied (via a password field). I got the signature fields to lock the form and I can unlock everything with a password dialog. However, I am trying to add some code to the Change event so that if a user clears their signature and no other signatures have been applied, then the form will unlock. I wrote a script that checks the signature validation of each signature field to verify that all of them are unsigned, and it works perfectly until one of the signature fields becomes hidden. Then the code just doesn't work. Am I doing something wrong? Is there a way to check if a signature field (which may or may not be hidden) has been signed? Below is the code that I am using:
var engMgrSig = event.target.getField("form1[0].Subform1[0].signatures[0].Eng_Manager[0].eng_manager_sign ature[0]").signatureValidate();
var mfgMgrSig = event.target.getField("form1[0].Subform1[0].signatures[0].Mfg_Eng_Manager[0].mfg_engr_sig nature[0]").signatureValidate();
if (mfgMgrSig == 0 && engMgrSig == 0)  {       
     oTargetField = this.resolveNode("ECO_table");
          oTargetField.access = "open";
else {
     oTargetField = this.resolveNode("ECO_table");
          oTargetField.access = "readOnly";

Answer 1

The fields are supposed to be hidden when the form is opened, but can be "added" (made visible) by the user to allow for additional signatures. I use hidden fields rather than a simple Add Instance because of data binding issues.
I tried modifying the script to make the fields visible, fire the validation, and then hidden again, but for some reason it would either not work or it would make them visible after the first change and then hidden only if the field was changed again. Also, the code has to be able to recognize whether the fields were hidden before the code fired. If the were, they should be hidden afterwards. If they weren't then nothing needs to happen to them.
I have tried using an IF statement to run a validation on the fields based on which ones are visible, but that doesn't seem to work either. Here is an example:
   // this field is always visible
    var status = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Eng_Manager[0].eng_manager _signature[0]").signatureValidate();
    var engMgrSig2 = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Eng_Manager2[0].eng_manage r_signature[0]").signatureValidate();
    var engMgrSig3 = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Eng_Manager3[0].eng_manage r_signature[0]").signatureValidate();
    // this field is always visible
    var mfgMgrSig1 = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Mfg_Eng_Manager[0].mfg_eng r_signature[0]").signatureValidate();
    var mfgMgrSig2 = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Mfg_Eng_Manager2[0].mfg_en gr_signature2[0]").signatureValidate();
    var mfgMgrSig3 = event.target.getField("form1[0].Subform1[0].signatures_REV1[0].Mfg_Eng_Manager3[0].mfg_en gr_signature3[0]").signatureValidate();
    //if all sig fields are visible
    if (this.resolveNode("signatures_REV1.Eng_Manager1").presence == "visible" && this.resolveNode("signatures_REV1.Eng_Manager3").presence == "visible" && this.resolveNode("signatures_REV1.Mfg_Eng_Manager2").presence == "visible" && this.resolveNode("signatures_REV1.Mfg_Eng_Manager3").presence == "visible") {
        if (status == 0 && mfgMgrSig1 == 0 && engMgrSig2 =0 && engMgrSig3 == 0 && mfgMgrSig2 == 0 && mfgMgrSig3 == 0)
            oTargetField = this.resolveNode("ECO_table");
                oTargetField.access = "open";           
    //if eng_mgr2 is visible
    if (this.resolveNode("form1.Subform1.signatures_REV1.Eng_Manager2").presence = "visible" && this.resolveNode("form1.Subform1.signatures_REV1.Eng_Manager3").presence = "hidden" && this.resolveNode("form1.Subform1.signatures_REV1.Mfg_Eng_Manager2").presence = "hidden" && this.resolveNode("form1.Subform1.signatures_REV1.Mfg_Eng_Manager3").presence = "hidden") {
       if (status == 0 && mfgMgrSig1 == 0 && engMgrSig2 =0)
            oTargetField = this.resolveNode("ECO_table");
                oTargetField.access = "open";