In BO there is a known procedure of open document connectivity which is used to drill from different BO reports with transfer of parameter values.
In my sample, I assume that we have a Webi report which was built over a SAP BW query with a variable on 0CALYEAR
(variable name is 0P_CALYE).
In order to get the right URL, you will need to get the Document link
Then you will get to the next screen
You need to copy the marked URL to notepad or any other text editor.
Next step will be to add to the end of the URL the following string &sType=wid&sRefresh=N&lsM0P_CALYE=YYYY
where the YYYY should be replaced with the desired year value.
Now all you need to do is call that URL from SAP Dashboard and transfer the year value dynamically to Webi.