Microsoft Crm 4.0 creating Workflow which fire on first day of month

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Microsoft

Hi Guys,

To create a workflow which fires on every month's first day. In this flow, calculate the total cost based on on formula, insert into invoice and update records. This workflow runs on every month's first day. Suppose flow starts in January then it will wait till 31st of January and work on 1st February. Must calculate the cost and create the invoice and update fields.

I am unable to find how to do this using workflow with Microsoft crm 4.0
please suggest.