Sql coldfusion error ( field not getting updated)

Hi,
  I am trying to insert some numeric data from a few form fields into the database table(MS SQL 2000). Now if one of those fields in blank it should not matter to me however it is trhowing me an error in such a case if a field or two is blank. I do not get such an error with the fields that are inserted into the varchar type in database.

Here is the error:

Error Executing Database Query.  
[Macromedia][SQLServer JDBC Driver][SQLServer]Error converting data type varchar to numeric.  
 
The error occurred in E:\docs_secure\icepe\act_update.cfm: line 133
Called from E:\docs_secure\icepe\act_update.cfm: line 1
Called from E:\docs_secure\icepe\act_update.cfm: line 133
Called from E:\docs_secure\icepe\act_update.cfm: line 1
 
131 :        voltage='#Form.voltage#',
132 :       calc_gpr_peak_asym='#Form.gprpeaka#'          
133 :    WHERE site_id='#Form.sid#'
134 : </CFQUERY>
135 : <cfelse>


Initially i did as follows which was not working

<cflock name="insertrecord_gpr" timeout="10">
<cfquery   datasource="sqldatas" username="****" password="***">
insert into gpr_info (grid_area, grid_resistance, gro_fau_duty, site_id, xr_ratio, voltage, calc_gpr_peak_asym)
values('#EVALUATE('form.gridarea')#','#EVALUATE('form.grid_resistance')#','#EVALUATE('form.gro_fau_duty')#','#EVALUATE('form.sid')#','#EVALUATE('form.xrratio')#'
,'#EVALUATE('form.voltage')#','#EVALUATE('form.gpr_asym')#')
</cfquery>
</cflock>

Then after some guidance from EE i did the folllowing but insert worked and update did not
This is what i did

Follwing update query did not work as it is not replacing(updating) the value with a blank or null when the user leves the value as blank in the submitting form field.

<CFQUERY datasource="sqldatas" name="updategpr" username="**** password="***">
   UPDATE gpr_info
   SET grid_area=<cfqueryparam value="#FORM.gridarea#" null="#iif( len( form.gridarea ), dE( "no" ), dE("yes" ) )#">,
   grid_resistance=<cfqueryparam value="#FORM.gridresist#" null="#iif( len( form.gridresist ), dE( "no" ), dE("yes" ) )#">,
      gro_fau_duty=<cfqueryparam value="#FORM.groduty#" null="#iif( len( form.groduty ), dE( "no" ), dE("yes" ) )#">,
      xr_ratio=<cfqueryparam value="#FORM.xrratio#" null="#iif( len( form.xrratio ), dE( "no" ), dE("yes" ) )#">,
       voltage=<cfqueryparam value="#FORM.voltage#" null="#iif( len( form.voltage ), dE( "no" ), dE("yes" ) )#">,
      calc_gpr_peak_asym=<cfqueryparam value="#FORM.gprpeaka#" null="#iif( len( form.gprpeaka ), dE( "no" ), dE("yes" ) )#">          
   WHERE site_id='#Form.sid#'
</CFQUERY>


However it works for insert as it enters blank or null in the database if i enter blank field in the submitting form

<cfquery datasource="sqldatas" username="****" password="****">
insert into gpr_info (grid_area, grid_resistance, gro_fau_duty, site_id, xr_ratio, voltage, calc_gpr_peak_asym)
values(<cfqueryparam value="#FORM.gridarea#" null="#iif( len( form.gridarea ), dE( "no" ), dE("yes" ) )#">,<cfqueryparam value="#FORM.gridresist#" null="#iif( len( form.gridresist ), dE( "no" ), dE("yes" ) )#">,<cfqueryparam value="#FORM.groduty#" null="#iif( len( form.groduty ), dE( "no" ), dE("yes" ) )#">,'#EVALUATE('form.sid')#',<cfqueryparam value="#FORM.xrratio#" null="#iif( len( form.xrratio ), dE( "no" ), dE("yes" ) )#">
,<cfqueryparam value="#FORM.voltage#" null="#iif( len( form.voltage ), dE( "no" ), dE("yes" ) )#">,<cfqueryparam value="#FORM.gprpeaka#" null="#iif( len( form.gprpeaka ), dE( "no" ), dE("yes" ) )#">)
</cfquery>

Thanks
Anup