Can anyone tell me what's wrong with the following "SetAll( "Dynamic.."..." call?

While setting the values - no problem. It's only on .refresh() of the grid, or when I click somewhere in the form that I get the error:

"Expression is invalid.  Use a valid expression for Dynamic..."

and I get it at least twice for each.

Select CENZNFLD		
If SEEK( lnCompID)
    Scan While AP_ID 	= lnAPID ;
         And   AP_FLD_ID 	= lnAPFldID
      lcFieldName	= ALLTRIM( FIELD_NAME)
      lnAPFactor	= AP_FACTOR
      Select csrZVARXACT
      Locate For ALLTRIM( FIELDNAME) = lcFieldName
      If FOUND()
	replace FIELDVAL With lnAPFactor In csrZVARXACT
      Endif 
    Endscan
    With Thisform.grdCenZoneFields
      .SetAll( "DynamicBackColor", "IIF( AP_FACTOR > 0, RGB( 0, 0, 255), RGB( 255, 255, 255))", "Column")  
      .SetAll( "DynamicForeColor", "IIF( AP_FACTOR > 0, RGB( 255, 255, 255), RGB( 0, 0, 255))", "Column")  
    Endwith 
Endif 

As far as I can ascertain the syntax is exactly as in Help, i.e.

frmMyForm.grdGrid1.SetAll("DynamicBackColor", "IIF(MOD(RECNO( ), 2)=0, ;
RGB(255,255,255), RGB(0,255,0))", "Column")  

Thanks

Terry