convert nvarchar to int
Here are some options.


CBool—Converts a value to a Boolean data type. 
CDate—Converts a value to a Date data type. 
CInt—Converts a value to an Integer data type.
CStr—Converts a value to a String data type. 
CVar—Converts a value to a Variant data type.


Syntax


CBool(expression)  
CByte(expression)
CCur(expression)
CDate(expression)  
CDbl(expression) 
CDec(expression) 
CInt(expression)    
CLng(expression)
CSng(expression)
CStr(expression)
CVar(expression)


Converting to an Integer Data Type

The CInt function takes a numeric or string value and converts it to an Integer data type. The argument is required and needs to represent a value within the range of -32,678 to 32,767. If the argument contains a decimal, Access rounds to the next whole number. A value of .5 or higher is rounded up; anything lower is rounded down. Some examples of CInt functions follow:

Dim MyDouble, MyInt
MyDouble = 2345.5678    ' MyDouble is a Double.
MyInt = CInt(MyDouble)    ' MyInt contains 2346.


IN SQL, you could use CAST.

SELECT
   CAST([Column] AS INT) AS [Column Name]
FROM [Table]
WHERE ...


Or, if you wanted to SUM off the SQL query.

SUM(CAST([Column] AS INT)) AS [Column Name]