Test to see if a worksheet is present

Using a for next loop I'm having excel create a new worksheet for every part number that is listed in a row on the main sheet. However I want to have it test to see if a worksheet of that name already exists and if it does, I want it to not create another worksheet of that name (which will bug) and resume on to it's next task.
Here is the foruma, any help would be appreciated:

For i = 1 To NumberofMDF

Worksheets("Part_Survey_Form").Activate
PLTnumber = Cells(8 + i, 1).Value
MFGnumber = Cells(8 + i, 2).Value

' here is where the question is
' Test to see if copy of MDF already exists.
If Worksheets("PLTnumber") = True Then
Resume



' Select sheet "Material Declaration Form" and makes a copy.
Sheets("Material Declaration Form").Select
Sheets("Material Declaration Form").Copy After:=Sheets(4)

' Change the new MDF sheet name to the P/N is for.
Sheets("Material Declaration Form (2)").Name = PLTnumber
Cells(11, 1).Value = PLTnumber
Cells(11, 2).Value = MFGnumber

' clears the cells to be able to enter new information
Range("C11:D11").Select
Selection.ClearContents
Range("D12:N29").Select
Selection.ClearContents
Range("A11").Select

Next i

use this function

it takes sheetname as the parameter

you can test by using

If check_sheets(PLTnumber) = True Then


Function check_sheet(s As String)
Dim wrk As Worksheet
Dim k As Integer
k = 0
For Each w In Worksheets
If w.Name = s Then
k = 1
End If
Next
If k = 1 Then
check_sheet = True
Else
check_sheet = False
End If
End Function