Convert String From Textbox To Int - SQL Code

How do I convert for example, a value comming from C# app "TextboxGBDataDeleted" to int column GBdatadeleted? I have a RangeValidator on this textbox to accept only numbers. I don't want to write C# code. I woul prefer to do this is SQL. Thank you.

My SQL update statement:

INSERT INTO KPITbl
(Lead, WRM, PTDB, PAR, PM, RequestingLOB, LOB, StartLocation, FinishLocation, Description, ProjectType, ServerName, ServerType, DCOorSTANDALONE, Responsible,
Status, RAG, StartDates, EndDates, TreeOrDomainImpacted, NumOfSites, NumOfUsers, GBdatamoved, GBdatadeleted, NumOfSrvrsAdded,
NumOfSrvrsDecommed, NumOfAppsDeployed, EUTEngineeringConsult, Comments, TimeSpend, Complexity, ECM, LastUpdated)
VALUES (@Lead,@WRM,@PTDB,@PAR,@PM,@RequestingLOB,@LOB,@StartLocation,@FinishLocation,@Description,@ProjectType,@ServerName,@ServerType,@DCOorSTANDALONE,@Responsible,@Status,@RAG,@StartDates,@EndDates,@TreeOrDomainImpacted,@NumOfSites,@NumOfUsers,@GBdatamoved,@GBdatadeleted,@NumOfSrvrsAdded,@NumOfSrvrsDecommed,@NumOfAppsDeployed,@EUTEngineeringConsult,@Comments,@TimeSpend,@Complexity,@ECM,(getdate() ) )

~~~~~~~~~~~~~~~~~~~~~~MY TABLE~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

CREATE TABLE [dbo].[KPITbl](
[TaskID] [int] IDENTITY(1,1) NOT NULL,
[Lead] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[WRM] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[PTDB] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[PAR] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[PM] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[RequestingLOB] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[LOB] [nvarchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[StartLocation] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[FinishLocation] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[Description] [nvarchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[ProjectType] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[ServerName] [nvarchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[ServerType] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[Responsible] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[Status] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[RAG] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[StartDates] [smalldatetime] NULL,
[EndDates] [smalldatetime] NULL,
[TreeorDomainImpacted] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[NumOfSites] [int] NULL,
[NumOfUsers] [int] NULL,
[GBdatamoved] [int] NULL,
[GBdatadeleted] [int] NULL,
[NumOfSrvrsAdded] [int] NULL,
[NumOfSrvrsDecommed] [int] NULL,
[NumOfAppsDeployed] [int] NULL,
[EUTEngineeringConsult] [nvarchar](max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[Comments] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[TimeSpend] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[Complexity] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[LastUpdated] [smalldatetime] NULL,
[DCOorSTANDALONE] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[ECM] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
[StatusCompletedDate] [smalldatetime] NULL,
[StatusCancelledDate] [smalldatetime] NULL,
CONSTRAINT [PK_Sheet1a] PRIMARY KEY CLUSTERED
(
[TaskID] ASC
)WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]