Create record via new windows

[JMart]

hi guys, 

Can someone point what I am doing wrong. the idea is to open a new windows and create a record on a related table. The windows name is based on the name of the button the users presses to open the window. the script I have is the following;

The issue I have is that once I add "set field [WO Notes::g_work_order_notes; ""] to clear the field for the next note I get the following error. 

 

 

any help is greatly appreciated. 

[OlgerDiekstra]

g_work_order_notes is not a global but a calculated field?