Exec In My Sp

I am trying to create a awkward sp, just need to know if i can do this somehow, here i piece of the code...

create procedure IM_SP_TrPreProc /*@TableName Varchar(255),*/ @SystemFileName Varchar(255)

---------------------------------------------
--Param1 = Tablename
--Param2 = Systemfilename
---------------------------------------------

as

declare @TableName Varchar(255);--Just For Testing---DELETE!!
declare @Filename varchar(255); --Store Distinct filename
declare @DSNo Varchar(255);-- Use 'set' to execute Var TableName
declare @SumUnits Varchar(255); --Use 'set' to calculate sum of units
declare @SumValue Varchar(255);
Set @TableName = 'TrDs01' -- Testing Only--DELETE!!

------------------------Set Statements using @TableName Var------------------------------------------

Set @DSNo = 'select distinct DataSupplierNo from ' + @TableName
Set @SumUnits = 'select sum(Units) from ' + @TableName
Set @SumValue = 'Select sum(Value) from ' + @TableName

------------------------------------------------------------------------------------------------------

Insert into TransactionMaster([FileName],DataSupplierNo,ImportFileRecordID,FileLoadDate,
UnitsSum,ValueSum,RecordCount)

Select(@Filename),(exec(DSNo)), ................

Just the Bold and underlined bit "exec(DSNo)"..... is this doable in some way? can i use exec to retrieve the value to insert to data supplier. As far as i know i have to do it like this because im using a variable as the table name...