Math Formula Node - Unable to parse m_expression Syntax error

Hey,

i’ve got a problem with the math formula node in Knime.

I’m using a javascript view node to create an calculator widget. In this widget i can create formulas like this as a flowvariable on output:

$column1$ - $column2$

I now want to use an math forumula node to use this formula to do the calculations based on widget input.

When i try to use the flow variable as an input to the node (“expression” field in the flow variable input of the math node) i get the following error: “Unable to parse m_expression Syntax error”

Do you have an idea what I’m doing wrong?

Does the expression field require an specific format? If yes, how do i change the format?

Best regards,

Jonah