Code expression for SUMPRODUCT

Good Morning Everyone,

I am stuck on getting the code expression right on a SUMPRODUCT function in my code for a project and could use some help. Here is my code that I need help with:

txtMultiplier.Value = Application.WorksheetFunction.SUMPRODUCT(--(txtCostEach>=Sheet4!(D5:D30),--(txtCostEach<=Sheet4!(E5:E30),Sheet4(F5:F30))

I am looking up the correct multiplier in order to multiply by the cost to determine ultimately the sell price for the part. Basically, if the cost each value is equal to or greater than the values in column D5 thru D30 and less then or equal to the value in Column E5:E30 it produces the appropriate Multiplier From Column F5:F30.

I have the formula calculating quite nicely on the worksheet, but can't seem to get the code expression right to make it functional in my code. Could anyone assist with the right expression?

Here is an example file of what I am trying to do: SUMPRODUCT Function Find Multiplier Example.xlsm

Thanks,
Larry