How to dynamically change a dimension from within a Member Function (in MDX) - ssas

Question

I've been having a hard time trying to figure out how to dynamically change a dimension from within a member function in MDX.
I have a fact table that contains 2 datetime fields (OperationDate and MeetingDate). I have a Power BI dashboard that has a date slicer which is based on the OperationDate. There's a matrix that has a summary of some measures (OpportunitiesCount, LostCount, WinCount, etc) that is being grouped by Sellers. Something like...
Date Slicer (this is based on OperationDate)
DateFrom: 2020-09-01
DateTo: 2020-09-30
<table>
<tr>
<th>SellerName</th>
<th>OpportunityCount</th>
<th>LostCount</th>
<th>WinCount</th>
<th>MeetingCount</th>
</tr>
<tr>
<td>SellerA</td>
<td>10</td>
<td>1</td>
<td>8</td>
<td>?</td>
</tr>
<tr>
<td>SellerB</td>
<td>12</td>
<td>0</td>
<td>2</td>
<td>?</td>
</tr>
<tr>
<td>SellerC</td>
<td>11</td>
<td>3</td>
<td>4</td>
<td>?</td>
</tr>
</table>
So the [OpportunityCount], [LostCount] and [WinCount] are based on OperationDate. The formulas for the first three columns are similar, but I'll take as an example the LostCount which goes somewhat like:
([Measures].[RowCount],[RowTypes].[Row Type].&[Lost])
At the UI level, the Date Slicer will do the math based on the OperationDate.
On the other hand, for the [Meeting] since it is based on MeetingDate, here's where I get stuck because I would think or thought that by borrowing the formula that I used for the first three columns it would be somewhat like:
([Measures].[RowCount],[RowTypes].[Row Type].&[Meeting])
But this would not give me the correct number since the Date Slicer is based on the OperationDate and not the MeetingDate.
Also I tried to create them from SSMS MDX editor as Member Functions but they are hard-coded. I would like them to be dynamic. In other words, at run-time if there's the possibility to swap dimensions (OperationDate and OptyMeetingDate).
Hardcoded way:
with MEMBER [Measures].[LostCountOperationDate] AS
sum(
(
[Measures].[RowCount]
,[RowTypes].[Row Type].&[Lost]
,([OperationDate].[FullYear].[Day].&[2020-09-01T00:00:00]:[OperationDate].[FullYear].[Day].&[2020-09-30T00:00:00])
)
)
MEMBER [Measures].[MeetingCountMeetingDate] AS
sum(
(
[Measures].[RowCount]
,[RowTypes].[Row Type].&[Meeting]
,([OptyMeetingDate].[FullYear].[Day].&[2020-09-01T00:00:00]:[OptyMeetingDate].[FullYear].[Day].&[2020-09-30T00:00:00])
)
)
QUESTION:
Is there a way to have something like...
with MEMBER [Measures].[RowCountOnAnyDateType] AS
sum(
(
[Measures].[RowCount]
,[RowTypes].[Row Type].&[Lost]
-- to have either dynamically OperationDate
,([OperationDate].[FullYear].[Day].&[2020-09-01T00:00:00]:[OperationDate].[FullYear].[Day].&[2020-09-30T00:00:00])
-- or OptyMeetingDate
,([OptyMeetingDate].[FullYear].[Day].&[2020-09-01T00:00:00]:[OptyMeetingDate].[FullYear].[Day].&[2020-09-30T00:00:00])
-- but has to be ONLY one of them based on the date range slicer selected at the UI
)
)
Thanks in advance,
Felix