Calculated field does not trigger workflows

Calculated field does not trigger workflows

Hi,

  I try to configure a workflow which will be triggered by a calculated field. I select that field when configuring the workflow. However, the workflow won't be trigger by the auto calculated field in the subform. 

  I have a subform with multiple field A, B, C, D, E and F. F is an auto calculated field for A+B+C+D+E (F=A+B+C+D+E). The calculation in the subform is working but the value in the F does not trigger the workflow. I need the workflow to trigger addition of subform from multiple row. 

  It will only work when I enable the field and manually update the field and trigger the workflow.

  Any help is much appreciated.

Thank you.