Basically, I created a function call responseComplete, and (in code) mimic'd loadComplete in set up. I then called responseComplete with the responseText from the server

Index: grid.base.js
===================================================================
--- grid.base.js        (revision 3438)
+++ grid.base.js        (working copy)
@@ -56,6 +56,7 @@
        onRightClickRow: null,
        onPaging: null,
        onSelectAll: null,
+       responseComplete: null,
        loadComplete: null,
        loadError: null,
        loadBeforeSend: null,
@@ -499,11 +500,12 @@
                var ts = this;
                $("
").insertBefore(this);
                $(this).attr({cellSpacing:"0",cellPadding:"0"});
-               var onSelectRow = this.p.onSelectRow, ondblClickRow = this.p.ondblClickRow, onSortCol=this.p.onSortCol, loadComplete = this.p.loadComplete, loadError = this.p.loadError, loadBeforeSend = this.p.loadBeforeSend;
+               var onSelectRow=this.p.onSelectRow, ondblClickRow=this.p.ondblClickRow, onSortCol=this.p.onSortCol, responseComplete=this.p.responseComplete, loadComplete=this.p.loadComplete, loadError=this.p.loadError, loadBeforeSend=this.p.loadBeforeSend;
                var onRightClickRow = this.p.onRightClickRow, afterInsRow = this.p.afterInsertRow;
                if(typeof onSelectRow !== 'function') {onSelectRow=false;}
                if(typeof ondblClickRow !== 'function') {ondblClickRow=false;}
                if(typeof onSortCol !== 'function') {onSortCol=false;}
+               if(typeof responseComplete !== 'function') {responseComplete=false;}
                if(typeof loadComplete !== 'function') {loadComplete=false;}
                if(typeof onRightClickRow !== 'function') {onRightClickRow=false;}
                if(typeof loadError !== 'function') {loadError=false;}
@@ -693,7 +695,7 @@
                                switch(ts.p.datatype)
                                {
                                case "json":
-                                       $.ajax({url:ts.p.url,type:ts.p.mtype,dataType:"json",data: gdata, complete:function(JSON,st) { if(st=="success") {addJSONData(eval("("+JSON.responseText+")"),ts.grid.bDiv); if(loadComplete) {loadComplete();}}}, error:function(xhr,st,err){if(loadError) {loadError(xhr,st,err);}endReq();}, beforeSend: function(xhr){if(loadBeforeSend) {loadBeforeSend(xhr);}}});
+                                       $.ajax({url:ts.p.url,type:ts.p.mtype,dataType:"json",data: gdata, complete:function(JSON,st) { if(st=="success") {if(responseComplete){addJSONData(responseComplete(JSON.responseText),ts.grid.bDiv);}else{addJSONData(eval("("+JSON.responseText+")"),ts.grid.bDiv);}  if(loadComplete) {loadComplete();}  } }, error:function(xhr,st,err){if(loadError) {loadError(xhr,st,err);}endReq();}, beforeSend: function(xhr){if(loadBeforeSend) {loadBeforeSend(xhr);}}});
                                        if( ts.p.loadonce || ts.p.treeGrid) {ts.p.datatype = "local";}
                                break;
                                case "xml":