Call PowerShell Script from PowerShell Script with multiple arguments

I know, this has been asked a few times but I cannot seem to get it working. Basically, I am using multiple ps1 files so I don't have to have a very large script, in this case, its two files (so far):

Migration-Main.ps1

Migration-Companies.ps1

I want to call Migration-Companies.ps1 from Migration-Main.ps1 using invoke expression but this seems to only work if there is only one parameter in the target script, in my case there are two:

param (
    [parameter(mandatory=$false )]
    [datetime]$CompanyDateCull,  
    [parameter(mandatory=$false )]
    [string]$CompanyManagerCull
)

Write-Output $CompanyDateCull

So if I try to call the script like so:

Invoke-Expression "$Script_Companies -CompanyDateCull $CompanyDateCull -CompanyManagerCull "Fred""

I will get the following result:

Invoke-Expression : A positional parameter cannot be found that accepts argument 'Fred'.
At C:\Users\user\OneDrive\Scripts\Migrations\Imports\FastTrack-Migration-Main.ps1:282 char:1
+ Invoke-Expression "$Script_Companies -CompanyDateCull $CompanyDateCul ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Invoke-Expression], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.PowerShell.Commands.InvokeExpressionCommand

But if i remove the second parameter

Invoke-Expression "$Script_Companies -CompanyDateCull $CompanyDateCull"

it works:

Saturday, 21 September 2013 12:00:00 AM

I have tried running the file with other commands as well, such as simply calling PowerShell.exe:

PowerShell.exe -file $Script_Companies -CompanyDateCull $CompanyDateCull -CompanyManagerCull $CompanyManagerCull

But this stops any of my dot sourced functions from being accessible to the script being called, which is a requirement.

Any help would be much appreciated.