Different where clause based on SSRS parameter
Yes, something like the below.

SELECT * 
FROM DataTable
WHERE (@SearchField = 'CreateDate' AND CreateDate BETWEEN @StartDate AND @EndDate)
OR (@SearchField = 'ModifyDate' AND ModifyDate BETWEEN @StartDate AND @EndDate)


Or, to use the example WHERE clauses you specified, how about the below?

SELECT *
FROM DataTable
WHERE (
        @ReportType = 1
        AND FundDatte &gt;= @FromDate
        AND FunDate &lt;= @ToDate
        )
    OR (
        @ReportType = 2
        AND DisbursementDate &gt;= @FromDate
        AND DisbursementDate &lt;= @ToDate
        )
    OR (
        @ReportType = 3
        AND (
            (
                FundDatte &gt;= @FromDate
                AND FunDate &lt;= @ToDate
                )
            AND (
                DisbursementDate &gt;= @FromDate
                AND DisbursementDate &lt;= @ToDate
                )
            )
        )