how to avoid copying to dhtmlx grid combo?

I have a grid xml:
Container No

<column  id="TareWt" width="10"  sort="str" type="edn"  align="left"  >Tare Wt.</column>
<column  id="MfgInfo" width="20"  sort="str" type="ed"  align="left"  >Mfg. Info</column>
<column  id="Class"  width="20" sort="str"  type="combo" filter="true"  
source="../DynamicData/JV_ASSET/Class.xml"  align="left" >
<column  id="Type"  width="20" sort="str"  type="combo" filter="true"  source="../DynamicData/JV_ASSET/Type.xml"  align="left" >

and I want to copy paste excel data on it without being able to affect combo type column? That is, the user must not paste on combo type columns rather just on SRN, TareWt and MfgInfo. How can I disable or Lock combo OR just diable clipboard to change my two combos above?