Assuming your report contains multiple records, I suppose this could work if the action was taken by clicking on a specific record. However, if using a button, there would be no "current" record since the button would get the focus, hence there'd be no filter. Speculation though, since I've never used a report to open a form. If you have to do it in this unusual fashion, consider passing the filter to the OpenArgs property of the report - IF you're not trying to open the form based on a single record in a report with many records. When you click the button, you can pass the report's OpenArgs to the opening form. Alternatively, I guess you could use a global variable, but IMHO, those should be avoided if there are better ways. I'd consider the OpenArgs property to be better.
If it is a multiple record report, then I have no idea, since AFAIK, this would be done by passing a selected record, which means you'd have to click on the record, not a button.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.