pass run time values in SQL

hii all

i need to run a sql statement on a database selected by the user at runtime

I am new to powershell please help

currently i am using

$Database = Read-Host -Prompt 'Input your Database  name'



invoke-sqlcmd -inputfile "C:\Users\tanveer.attar\Desktop\script\maintainance\synch_mdf\synchmdf.sql" -serverinstance "myserver" -Database $Database

use DATABASENAME
declare @MinimumSpace int,@SpaceAllocated int
select @MinimumSpace = convert(decimal(12,2),round(fileproperty([name],'SpaceUsed')/128.000,2))
from dbo.sysfiles where fileid=1
set @SpaceAllocated=@MinimumSpace+50
ALTER DATABASE [DATABASENAME] SET RECOVERY SIMPLE WITH NO_WAIT
DBCC SHRINKFILE (N'DATABASENAME', @SpaceAllocated)
ALTER DATABASE [DATABASENAME] SET RECOVERY FULL WITH NO_WAIT

how do i execute this sql statement accounding to the db names entered by users

tanveer