SSRS Adding DYNAMIC SCOPE to Expression Formula in Report?

Here is an example of my current formula that I'm having an issue in ADDING SCOPE. Is it possible to use DYNAMIC SCOPE in a formula like this?

The issue is when I run my report for ALL GROUPS, this formula displays incorrect percentages, but when I select a single customer within the group, the percentages are correct....

=Sum(CDEC(Fields!Status_Complete.Value), "Status")/Count(Fields!Status_Complete.Value, "Status")

Can someone help with advising how to add a GROUP scope to this above formula?
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MIKESoftware Solutions ConsultantAsked:
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lcohanDatabase AnalystCommented:
I believe this "Deciding Whether to Use an Expression or a Variable in SSRS" should help to understand the difference between cell/box and group:

And definitely please read "Understanding Group Membership for Tablix Cells":

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