Here are the combinations...
PA1 + PB1+ PC1 + PD1
PA1 + PB1+ PC1 + PD2
PA1 + PB2+ PC1 + PD1
PA1 + PB2+ PC1 + PD2
PA1 + PB3+ PC1 + PD1
PA1 + PB3+ PC1 + PD2
PA2 + PB1+ PC1 + PD1
PA2 + PB1+ PC1 + PD2
PA2 + PB2+ PC1 + PD1
PA2 + PB2+ PC1 + PD2
PA2 + PB3+ PC1 + PD1
PA2 + PB3+ PC1 + PD2
PA3 + PB1+ PC1 + PD1
PA3 + PB1+ PC1 + PD2
PA3 + PB2+ PC1 + PD1
PA3 + PB2+ PC1 + PD2
PA3 + PB3+ PC1 + PD1
PA3 + PB3+ PC1 + PD2
PA4 + PB1+ PC1 + PD1
PA4 + PB1+ PC1 + PD2
PA4 + PB2+ PC1 + PD1
PA4 + PB2+ PC1 + PD2
PA4 + PB3+ PC1 + PD1
PA4 + PB3+ PC1 + PD2

....and here is the code that generates them:
Sub Combinations()
Dim PA As Byte
Dim PB As Byte
Dim PD As Byte

For PA = 1 To 4
For PB = 1 To 3
For PD = 1 To 2
ActiveCell.Value = "PA" & PA & " + PB" & PB & "+ PC1 + PD" & PD
ActiveCell.Offset(1, 0).Select
Next PD
Next PB
Next PA

End Sub