I have a script that populates the Commission Plan on the Invoice detail line from what is selected on the header.  The script is quite simple:

Form.Controls("cboCommPlanDtl").text = Form.Controls("cboCommPlan").text

and works perfectly as long as there is something selected in the Commission Plan field on the header.  

Since not all of the invoices have Salespeople associated, the commission plan is sometime not populated  When that's the case, I get an error that says "clsScriptMgr.ExecuteScript:  'Text'property is read only."

I have tried doing a conditional statement, and the script says it's valid, but it doesn't seem to work.  It doesn't seem to like the .text  when that field is null.  Any suggestions or thoughts on how to handle the null plan values.  

Thank you!