Ignition Script - identify the Initial execution


I have a display time based script to assign the following Stored Procedure input parameter to None initially (1st execution).
prodFamilyCode = None

call = system.db.createSProcCall(“dbo.spLocal_EY_OpEx_Get_T1_PM_Quality_Data_QualityTest”,“PA_Prod”)
call.registerInParam(1, system.db.VARCHAR, Language)
call.registerInParam(2, system.db.VARCHAR, LineTeamArea)
call.registerInParam(3, system.db.VARCHAR, Line)
call.registerInParam(4, system.db.VARCHAR, Equipment)
call.registerInParam(5, system.db.VARCHAR, Endtime)
call.registerInParam(6, system.db.VARCHAR, DayWeek)
call.registerInParam(7, system.db.VARCHAR, prodFamilyCode)
call.registerInParam(8, system.db.VARCHAR, resulttype)

The stored procedure will return a list of the Product Family and populate to a Drop down list.
A default (preferred) Product Family will be selected as the ‘Selected Label’ of the drop down list.

From this time onwards, the display script will run every 10 secs to update the table grid.
I don’t want the prodFamilyCode to be None anymore.
It should use the ‘selected label’ from the dropdown list.

How can I detect the initial execution of the display script to assign the prodFamilyCode = None ?
And all the subsequent executions will use the value from the ‘Selected Label’ from the drop down list.

When the operator changes the drop down list, I have another property change script to update the table. That’s fine and it’s working.

The issue is at the display time based script running every 10 sec and I don’t want the prodFamilyCode to be ‘None’ again after the initial execution.

I am so sorry that I am new to the ignition. I would be appreciated any one of you can give me some inputs.